This blog has long been a fan of Kari Lehtonen, who was dealt yesterday to the Dallas Stars for a prospect and a 4th round pick. I've made the case for Lehtonen in a couple of places, but the basic argument is that between his stints on the IR he has put together some pretty persuasive evidence of being a terrific puckstopper.
Even Strength Save Percentage Leaders Since the Lockout (min. 200 GP):
1. Tomas Vokoun: 282 GP, .935
2. Roberto Luongo: 328 GP, .930
3. Tim Thomas: 250 GP, .927
3. J.S. Giguere: 243 GP, .927
5. Miikka Kiprusoff: 353 GP, .926
5. Martin Brodeur: 314 GP, .926
7. Henrik Lundqvist: 316 GP, .925
7. Kari Lehtonen: 200 GP, .925
9. Ilya Bryzgalov: 238 GP, .924
9. Ryan Miller: 296 GP, .924
That is some heady company for Lehtonen to be keeping. However, it's not all positive for the young Finn. There are certainly question marks. The injuries, of course. Consistent rumours out of Atlanta questioning Lehtonen's motivation, conditioning and commitment. PK save % numbers that are nothing special and well below the rest of the above group. His shots against, which have been consistently higher than his playing partners, implying that his skill in terms of goal prevention may be slightly lower than his save percentage implies.
Dallas gave up one of their better prospects, which may indicate they have some long-term plans for Lehtonen. Changes of scenery can often be beneficial for athletes with elite potential but questionable work ethic. With Alex Auld and Marty Turco still in the mix in Dallas, Lehtonen will have to work hard to be able to play.
It's impossible to predict whether Lehtonen's injury woes are in the past or something that will continue to plague him throughout his NHL career. Nevertheless, if I was Dallas I'd probably rather bet my team's playoff chances on Lehtonen than on the apparently washed-up Marty Turco. It will be interesting to see how Lehtonen does in Dallas. I think he has a good chance of success.
I'll also be staying tuned to see the shots against numbers for Lehtonen as a Star, especially compared to Turco. We'll see what the gap is between a guy who has a track record of facing more shots than his teammates and one of the top puckhandlers in the league. That figure could shed more light on the boundaries of shot effects for NHL goalies.
Wednesday, February 10, 2010
Tuesday, February 2, 2010
The Hogwash of "Big Saves"
Let's do a thought experiment where we imagine a goalie who is perfect and has the ability to stop every single shot he faces. That's because he is so athletic, or so big, or because he can read shooters' minds, or however else you want to imagine the hypothetical. His skills have only one limitation, they don't apply in shootouts because shootouts have nothing to do with the rest of the game of hockey. This goalie's skill is average in shootouts and as a result his team has the same 50% chance of winning a shootout as anybody else.
The goalie also happens to be an attention seeker and a thrill junkie, who loves pressure situations. He doesn't care at all about personal stats, only whether his team wins the game or not. His team is in a non-traditional hockey market and is struggling to sell tickets. As a result, the owner wants to have every game be as exciting as possible to boost the gate receipts.
The owner has discussed strategy with the goalie, and they have agreed that the goalie will adjust his effort to try to make every game as close as possible, but at the same time never intentionally throwing a game. They decide it is also best not to tell the team's coach of this plan, since the owner is thinking of firing him at the end of the season and doesn't want the media or the league to find out that his team is in effect shaving points.
Since he doesn't know he has a goalie with super powers, the coach does not use any all-out offensive strategies that might make sense in such a scenario (aggressive forechecking, playing with four or five forwards, using cherry-pickers, etc.). Instead he plays a typical offensive system, and the team is about average offensively.
What does the goalie do in this scenario? Obviously he can freely give up goals when his team is ahead by 2 goals or more, because he can then shut the door and preserve the one goal margin. What about if his team is leading by a single goal? If there is little time left in the game, then it is unlikely that his team will score again. A shootout brings a 50% chance of losing, so if the goalie intentionally gives up a goal late in the game when ahead by one there is an even money chance that he is costing his team a win. Earlier in the game it is more likely that the goalie's team will score again to retake the lead, but nothing is guaranteed since hockey is a low-scoring game.
If he wants his team to pick up two points in every game, the goalie can't risk giving up any lead at all. There are some situations where the gambling odds might be pretty favourable, such as playing at home against a weak opponent where his team goes up 1-0 early in the first period. But give up enough goals in those scenarios and eventually there will be a game that will remain tied and be lost in a shootout.
By similar logic, the goalie can't give up a goal when the game is tied. In fact, that is considerably more crucial than allowing a goal when his team is ahead. A tie game is at least guaranteed to earn a loser point from going to a shootout, but if the team is trailing they need a goal just to force a shootout and face the prospect of a regulation loss if they aren't able to score again.
So this goalie, even if he is really daring, will probably never allow the first goal against and will most often just wait until his team scores 2 or 3 goals before he starts letting some in. He might for fun let in a goal or two early in the game against a bad team, or let the other team tie it up at 1-1 or 2-2 early in the game if he's pretty sure his teammates can score again. Despite giving up as many goals as he can he'll still probably lead the league in GAA and have a very high save percentage.
Now let's revise the scenario to make it a little more realistic. Some goals in hockey are just unstoppable by any goalie because they come on deflections, screens, lucky bounces, great setups, or shots that are simply too fast and too perfectly placed for anyone to stop. Let's assume that on average there is one goal against per game the goalie can't do anything about. These goals occur randomly and without any regularity. Sometimes the goalie goes several games in a row without allowing any, and sometimes he lets in 2 or 3 of them in the same game. How does that change his strategy, given his objective of not trying when his team is very likely to win yet still winning every game possible?
The answer is that now the goalie will essentially have to try to stop everything unless his team is up by 2 goals or more. Even if they are ahead by 2, he could end up blowing the lead by messing around and giving up a goal for fun which is then followed immediately by another one on an unlucky bounce. Similarly, he wouldn't want to intentionally let the other team tie the game because there is always the chance they will then take the lead on an unstoppable shot.
If his team scores 0, 1 or 2 goals in the game (which happens 47% of the time on average) the goalie will likely try to stop every shot he faces. If the team scores 3 or 4 goals (which happens 38% of the time on average), the goalie might let in one or two intentionally. About 14% of the time the team will score 5+ goals, and in that case the goalie can let in some goals for fun.
Multiply out the probabilities of the team's goal support with the expected intentional goals the goalie might allow, and the average would be about one intentional goal against per game. So if a goalie was trying to win every game while simultaneously never trying to stop the puck when he didn't have to, his goals against would be about one goal higher than it would otherwise be. That is, a save percentage of close to .000 when it doesn't matter would equal a GAA increase of about one.
I think it's pretty clear that under any even remotely realistic assumptions about how much a goalie is going to be goofing off when his team has the game in hand that the GAA effect is going to be very minimal, unless the goalie is playing on some kind of dynasty that is always blowing out the opposition. And even then it's certainly no positive trait in my book that a goalie doesn't care whether or not he gets scored on, even if his team is well in front.
It remains possible that there may be slight differences in team performance because of differences in goalie success in high-leverage situations. But I'm not convinced that is either significant or based on repeatable skill. If it exists it will create a slight difference between goalies with similar performance levels, but there is simply no way that a goalie like Marc-Andre Fleury (.907 career save percentage) is doing more to help his team win than a Tomas Vokoun (.917), regardless of career win/loss records.
I think the basic problem behind this common misconception is that people consistently overestimate the level of control a goalie has over his own play and the number of goals against. Vic Ferrari writes constantly about how hockey is a game of luck, and that's really true. Yet fans have heard lots of stuff about how goaltending is such a mental game, so they think that a goalie in the proper mental state can just decide to make himself unbeatable. Either that or or they give too much credence to one of those overplayed stories where Patrick Roy or somebody stood up in the dressing room and said, "Get me one more goal, boys, because I'm not letting in another one." He probably said that almost every time they were tied after two periods in the playoffs, and needless to say his team did not always win the game.
Sometimes the shooters make their shots, that's a fundamental basic truth of goaltending. It's not always the goalie's fault that the puck hits the back of the net. Anyone who wants to be a goalie or who wants to properly evaluate goaltending needs to be aware of that simple fact, or you're evaluating the luck-soaked result instead of the skill-based process.
If there exist some goals that are unstoppable and a goalie can't predict his team's future offence, which are two basic assumptions that obviously hold in hockey, there really is very little opportunity for a goalie to mess with the scoreline without costing his team. And that is why attempts to explain away poor individual save statistics with references to a goalie's win total are just biased nonsense.
Long story short, the next time you hear an announcer say something like, "It's not how many saves you make, it's when you make them", what he's actually telling you is, "I have no idea how to separate the contribution of a goalie from the contribution of the rest of the team."
The goalie also happens to be an attention seeker and a thrill junkie, who loves pressure situations. He doesn't care at all about personal stats, only whether his team wins the game or not. His team is in a non-traditional hockey market and is struggling to sell tickets. As a result, the owner wants to have every game be as exciting as possible to boost the gate receipts.
The owner has discussed strategy with the goalie, and they have agreed that the goalie will adjust his effort to try to make every game as close as possible, but at the same time never intentionally throwing a game. They decide it is also best not to tell the team's coach of this plan, since the owner is thinking of firing him at the end of the season and doesn't want the media or the league to find out that his team is in effect shaving points.
Since he doesn't know he has a goalie with super powers, the coach does not use any all-out offensive strategies that might make sense in such a scenario (aggressive forechecking, playing with four or five forwards, using cherry-pickers, etc.). Instead he plays a typical offensive system, and the team is about average offensively.
What does the goalie do in this scenario? Obviously he can freely give up goals when his team is ahead by 2 goals or more, because he can then shut the door and preserve the one goal margin. What about if his team is leading by a single goal? If there is little time left in the game, then it is unlikely that his team will score again. A shootout brings a 50% chance of losing, so if the goalie intentionally gives up a goal late in the game when ahead by one there is an even money chance that he is costing his team a win. Earlier in the game it is more likely that the goalie's team will score again to retake the lead, but nothing is guaranteed since hockey is a low-scoring game.
If he wants his team to pick up two points in every game, the goalie can't risk giving up any lead at all. There are some situations where the gambling odds might be pretty favourable, such as playing at home against a weak opponent where his team goes up 1-0 early in the first period. But give up enough goals in those scenarios and eventually there will be a game that will remain tied and be lost in a shootout.
By similar logic, the goalie can't give up a goal when the game is tied. In fact, that is considerably more crucial than allowing a goal when his team is ahead. A tie game is at least guaranteed to earn a loser point from going to a shootout, but if the team is trailing they need a goal just to force a shootout and face the prospect of a regulation loss if they aren't able to score again.
So this goalie, even if he is really daring, will probably never allow the first goal against and will most often just wait until his team scores 2 or 3 goals before he starts letting some in. He might for fun let in a goal or two early in the game against a bad team, or let the other team tie it up at 1-1 or 2-2 early in the game if he's pretty sure his teammates can score again. Despite giving up as many goals as he can he'll still probably lead the league in GAA and have a very high save percentage.
Now let's revise the scenario to make it a little more realistic. Some goals in hockey are just unstoppable by any goalie because they come on deflections, screens, lucky bounces, great setups, or shots that are simply too fast and too perfectly placed for anyone to stop. Let's assume that on average there is one goal against per game the goalie can't do anything about. These goals occur randomly and without any regularity. Sometimes the goalie goes several games in a row without allowing any, and sometimes he lets in 2 or 3 of them in the same game. How does that change his strategy, given his objective of not trying when his team is very likely to win yet still winning every game possible?
The answer is that now the goalie will essentially have to try to stop everything unless his team is up by 2 goals or more. Even if they are ahead by 2, he could end up blowing the lead by messing around and giving up a goal for fun which is then followed immediately by another one on an unlucky bounce. Similarly, he wouldn't want to intentionally let the other team tie the game because there is always the chance they will then take the lead on an unstoppable shot.
If his team scores 0, 1 or 2 goals in the game (which happens 47% of the time on average) the goalie will likely try to stop every shot he faces. If the team scores 3 or 4 goals (which happens 38% of the time on average), the goalie might let in one or two intentionally. About 14% of the time the team will score 5+ goals, and in that case the goalie can let in some goals for fun.
Multiply out the probabilities of the team's goal support with the expected intentional goals the goalie might allow, and the average would be about one intentional goal against per game. So if a goalie was trying to win every game while simultaneously never trying to stop the puck when he didn't have to, his goals against would be about one goal higher than it would otherwise be. That is, a save percentage of close to .000 when it doesn't matter would equal a GAA increase of about one.
I think it's pretty clear that under any even remotely realistic assumptions about how much a goalie is going to be goofing off when his team has the game in hand that the GAA effect is going to be very minimal, unless the goalie is playing on some kind of dynasty that is always blowing out the opposition. And even then it's certainly no positive trait in my book that a goalie doesn't care whether or not he gets scored on, even if his team is well in front.
It remains possible that there may be slight differences in team performance because of differences in goalie success in high-leverage situations. But I'm not convinced that is either significant or based on repeatable skill. If it exists it will create a slight difference between goalies with similar performance levels, but there is simply no way that a goalie like Marc-Andre Fleury (.907 career save percentage) is doing more to help his team win than a Tomas Vokoun (.917), regardless of career win/loss records.
I think the basic problem behind this common misconception is that people consistently overestimate the level of control a goalie has over his own play and the number of goals against. Vic Ferrari writes constantly about how hockey is a game of luck, and that's really true. Yet fans have heard lots of stuff about how goaltending is such a mental game, so they think that a goalie in the proper mental state can just decide to make himself unbeatable. Either that or or they give too much credence to one of those overplayed stories where Patrick Roy or somebody stood up in the dressing room and said, "Get me one more goal, boys, because I'm not letting in another one." He probably said that almost every time they were tied after two periods in the playoffs, and needless to say his team did not always win the game.
Sometimes the shooters make their shots, that's a fundamental basic truth of goaltending. It's not always the goalie's fault that the puck hits the back of the net. Anyone who wants to be a goalie or who wants to properly evaluate goaltending needs to be aware of that simple fact, or you're evaluating the luck-soaked result instead of the skill-based process.
If there exist some goals that are unstoppable and a goalie can't predict his team's future offence, which are two basic assumptions that obviously hold in hockey, there really is very little opportunity for a goalie to mess with the scoreline without costing his team. And that is why attempts to explain away poor individual save statistics with references to a goalie's win total are just biased nonsense.
Long story short, the next time you hear an announcer say something like, "It's not how many saves you make, it's when you make them", what he's actually telling you is, "I have no idea how to separate the contribution of a goalie from the contribution of the rest of the team."
Thursday, January 28, 2010
Shots Against
This is just a short post on a little idea I had a while back and have been meaning to get around to doing. It's on the topic of the relationship between save percentage and shots against. One way to put a team in the best possible context is to look at other teams in the league that are similar. For example, if it is easier to play goalie on a team that allows a lot of shots against then it is likely that other teams with a similar shot profile would have the same advantage.
I looked at the situational save percentage numbers for the five teams that were closest in shots against per 60 minutes to the New Jersey Devils and the Florida Panthers from 2003-04 to 2008-09. New Jersey and Florida are two teams that are often brought up when various theories are advanced about whether the number of shots per game a goalie faces has an effect on their save percentage. I also reran the numbers using a few possible shot bias/goalie shot effect adjustments (adding one shot and two shots to New Jersey's totals and subtracting one from Florida's).
The result? There doesn't seem to be any significant effects from different levels of shots. If either of the teams are outliers then they also stand out against teams with similar shot prevention.
League average: .918 EV SV%, .866 PK SV%, .912 PP SV%
I looked at the situational save percentage numbers for the five teams that were closest in shots against per 60 minutes to the New Jersey Devils and the Florida Panthers from 2003-04 to 2008-09. New Jersey and Florida are two teams that are often brought up when various theories are advanced about whether the number of shots per game a goalie faces has an effect on their save percentage. I also reran the numbers using a few possible shot bias/goalie shot effect adjustments (adding one shot and two shots to New Jersey's totals and subtracting one from Florida's).
The result? There doesn't seem to be any significant effects from different levels of shots. If either of the teams are outliers then they also stand out against teams with similar shot prevention.
League average: .918 EV SV%, .866 PK SV%, .912 PP SV%
| Team | Adjustment | EV SV% | PK SV% | PP SV% |
| New Jersey | 0 | .918 | .868 | .906 |
| New Jersey | +1 | .916 | .865 | .918 |
| New Jersey | +2 | .919 | .865 | .915 |
| Florida | 0 | .916 | .867 | .913 |
| Florida | -1 | .916 | .865 | .911 |
Tuesday, January 26, 2010
Three Stars
I bash the media a lot in this space, but sometimes it is interesting to see what they have to say. For Puck Prospectus I put together a look at three star selections for goalies.
I just quickly looked up the same numbers last year for Steve Mason, because I'm interested by how seasonal statistics like GAA and shutouts can have a huge impact on perceptions. Fans and media personnel who watch the games can be unimpressed by a goaltender night after night over long stretches of the season, but come April the number of wins and shutouts in the goalie's stat line might lead them to quite a different conclusion. If you watch a goalie make 18 easy saves against the Carolina Hurricanes on a Tuesday night in November, you might think that was a pretty meaningless shutout. Months later, when your memories of that game have faded and you are trying to decide which goalies to put on your Vezina ballot, that shutout might make the difference between that goalie or someone else.
Mason's three star voting numbers in 2008-09 fell right in line with his save percentages. He was lights-out in December (.950 save %, named one of the game's three stars 8 times in 11 starts), but was mediocre for the rest of the season (.905 save %, named a game star in just 10 out of 41 starts). Over the entire season Mason was named a star of the game in 34% of his starts, which is pretty good but not anything unusual since the average for goalies is about 30% of the time.
For three and half months Mason's play was subpar and those watching certainly weren't being amazed by what they saw. Yet because of his terrific work earlier in the year, every time they looked at a stat sheet they saw a pretty low GAA, a decent win total and most notably a lot of shutouts. The result was a widespread perception that Mason carried the Blue Jackets into the playoffs, earning him a flat-out ridiculous 4th place finish in Hart Trophy voting.
I just quickly looked up the same numbers last year for Steve Mason, because I'm interested by how seasonal statistics like GAA and shutouts can have a huge impact on perceptions. Fans and media personnel who watch the games can be unimpressed by a goaltender night after night over long stretches of the season, but come April the number of wins and shutouts in the goalie's stat line might lead them to quite a different conclusion. If you watch a goalie make 18 easy saves against the Carolina Hurricanes on a Tuesday night in November, you might think that was a pretty meaningless shutout. Months later, when your memories of that game have faded and you are trying to decide which goalies to put on your Vezina ballot, that shutout might make the difference between that goalie or someone else.
Mason's three star voting numbers in 2008-09 fell right in line with his save percentages. He was lights-out in December (.950 save %, named one of the game's three stars 8 times in 11 starts), but was mediocre for the rest of the season (.905 save %, named a game star in just 10 out of 41 starts). Over the entire season Mason was named a star of the game in 34% of his starts, which is pretty good but not anything unusual since the average for goalies is about 30% of the time.
For three and half months Mason's play was subpar and those watching certainly weren't being amazed by what they saw. Yet because of his terrific work earlier in the year, every time they looked at a stat sheet they saw a pretty low GAA, a decent win total and most notably a lot of shutouts. The result was a widespread perception that Mason carried the Blue Jackets into the playoffs, earning him a flat-out ridiculous 4th place finish in Hart Trophy voting.
Friday, January 22, 2010
High and Low Shot Games
I looked at low shot games in one of my Puck Prospectus articles from earlier this year, and I wanted to look at those games in a bit more detail. I took a sample of this season's games with the most and the least shots taken by one of the teams. For the most shots, I took the 40 highest totals, while for the least shots I took the top 38 (to avoid ties that would have extended the sample well past 40).
Here are some of the numbers:
Shooting Percentage by Period:
1st period: High Shot 4.3%, Low Shot 14.6%
2nd period: High Shot 5.8%, Low Shot 8.7%
3rd period: High Shot 7.6%, Low Shot 10.4%
These numbers really show how a team's shooting percentage (or, conversely, the opposing goalie's save percentage) impacts the number of shots in the game. A high save percentage tends to cause higher shots against, while a lower save percentage tends to cause lower shots against.
I did not remove empty net goals. If I had done so, I'd guess that both the high and low shot teams would have had third period numbers that were more similar to their second period results.
The low shot teams shot the lights out in the first period, and then probably scored at about the the league average rate for the next two periods (excluding likely empty-netters). This indicates fairly strongly that the direction of causation runs from the percentages to the totals, rather than the other way around. The high shot teams scored at a below-average rate throughout the game, suggesting that very high shots against numbers do tend to go hand in hand with a high save percentage (although it could still be that an outstanding goalie performance is usually required for a team to take that many shots).
If the game score had a strong effect on the numbers, then that should show up in a breakdown of shots against by period:
Percentage of Shots by Period:
1st period: High Shot 31.6%, Low Shot 32.6%
2nd period: High Shot 32.7%, Low Shot 38.4%
3rd period: High Shot 32.5%, Low Shot 27.4%
Overtime: High Shot 3.2%, Low Shot 1.6%
The third period is when we would expect to see the strongest playing to the score effects. The third period is when the least shots were taken in low shot games. This again supports the theory that low shot games are usually a result of the scoreline and the percentages early in the game.
In contrast teams with high shot totals did not show any playing to the score effect, at least on the offensive side.
I also thought to look at the shots broken down by game situation, to see whether power play or shorthanded situations might have had a significant impact.
Shooting Percentage by Game Situation:
5 on 5: High Shot 5.1%, Low Shot 10.6%
5 on 4: High Shot 7.2%, Low Shot 12.8%
4 on 4: High Shot 7.8%, Low Shot 10.0%
4 on 5: High Shot 7.7%, Low Shot 16.7%
Percentage of Shots by Game Situation:
5 on 5: High Shot 73.1%, Low Shot 76.2%
5 on 4: High Shot 19.0%, Low Shot 14.9%
4 on 4: High Shot 4.1%, Low Shot 4.8%
4 on 5: High Shot 2.1%, Low Shot 2.9%
The low shot teams had a higher shooting percentage at all four game situations. In my view this supports the theory that shooting percentage has a strong impact on shots against. I suspect there may be some shot quality effect at even strength related to shots against. For example, the team that is taking more shots will likely be also taking more from the less dangerous scoring areas, and more of their shots will come from third/fourth liners and defencemen. However, it seems unlikely to me that a goalie would perform worse while shorthanded or on the power play simply because of a low overall number of shots against in the game.
I had a theory that one of the reasons that goalies often put up low save percentages when not facing very many shots was that they faced a higher percentage of power play shots. It turns out that the exact opposite was true, at least in 2009-10. One of the reasons that those teams took few shots in the first place was that they did not tend to have very many power play opportunities. The high shot teams had a situational distribution that is very similar to the overall average.
It seems apparent that save percentage has an impact on shots against. Teams that posted high shot totals tended to have very low shooting percentages early in the game, while the opposite is true for teams with low shot totals. There does appear to be some relationship between high shots against and a higher save percentage, although it is still somewhat uncertain how much that has to do with a potential shot quality effect and how much the shots against are caused by the high save percentage.
A very high shots against total tends to come in games where one team is significantly better than the other and where the better team has some incentive to keep playing for 60 minutes (i.e. the score is close or the team being outshot has the lead). That is usually only possible when the goalie on the weaker team is having a good day. After all, if the better team gets 3 or 4 goals and builds a comfortable lead then they usually shut it down somewhat and don't end up hitting the 40+ shot range.
It may be possible that goalies on weak teams get more chances to pad their stats with 40+ shots against games where a lot of the shots are of relatively low quality. It is possible that this counterbalances the likelihood that bad teams would tend to give up higher numbers of scoring chances against. I think more analysis needs to be done to determine whether there is an overall effect. All studies I've seen that look at seasonal averages for all teams show no relationship between save percentage and shots against, so I don't doubt that for most teams it all comes out even in the wash, but it remains to be seen whether there are unusual effects on outlying teams such as the Panthers or the Devils.
Here are some of the numbers:
Shooting Percentage by Period:
1st period: High Shot 4.3%, Low Shot 14.6%
2nd period: High Shot 5.8%, Low Shot 8.7%
3rd period: High Shot 7.6%, Low Shot 10.4%
These numbers really show how a team's shooting percentage (or, conversely, the opposing goalie's save percentage) impacts the number of shots in the game. A high save percentage tends to cause higher shots against, while a lower save percentage tends to cause lower shots against.
I did not remove empty net goals. If I had done so, I'd guess that both the high and low shot teams would have had third period numbers that were more similar to their second period results.
The low shot teams shot the lights out in the first period, and then probably scored at about the the league average rate for the next two periods (excluding likely empty-netters). This indicates fairly strongly that the direction of causation runs from the percentages to the totals, rather than the other way around. The high shot teams scored at a below-average rate throughout the game, suggesting that very high shots against numbers do tend to go hand in hand with a high save percentage (although it could still be that an outstanding goalie performance is usually required for a team to take that many shots).
If the game score had a strong effect on the numbers, then that should show up in a breakdown of shots against by period:
Percentage of Shots by Period:
1st period: High Shot 31.6%, Low Shot 32.6%
2nd period: High Shot 32.7%, Low Shot 38.4%
3rd period: High Shot 32.5%, Low Shot 27.4%
Overtime: High Shot 3.2%, Low Shot 1.6%
The third period is when we would expect to see the strongest playing to the score effects. The third period is when the least shots were taken in low shot games. This again supports the theory that low shot games are usually a result of the scoreline and the percentages early in the game.
In contrast teams with high shot totals did not show any playing to the score effect, at least on the offensive side.
I also thought to look at the shots broken down by game situation, to see whether power play or shorthanded situations might have had a significant impact.
Shooting Percentage by Game Situation:
5 on 5: High Shot 5.1%, Low Shot 10.6%
5 on 4: High Shot 7.2%, Low Shot 12.8%
4 on 4: High Shot 7.8%, Low Shot 10.0%
4 on 5: High Shot 7.7%, Low Shot 16.7%
Percentage of Shots by Game Situation:
5 on 5: High Shot 73.1%, Low Shot 76.2%
5 on 4: High Shot 19.0%, Low Shot 14.9%
4 on 4: High Shot 4.1%, Low Shot 4.8%
4 on 5: High Shot 2.1%, Low Shot 2.9%
The low shot teams had a higher shooting percentage at all four game situations. In my view this supports the theory that shooting percentage has a strong impact on shots against. I suspect there may be some shot quality effect at even strength related to shots against. For example, the team that is taking more shots will likely be also taking more from the less dangerous scoring areas, and more of their shots will come from third/fourth liners and defencemen. However, it seems unlikely to me that a goalie would perform worse while shorthanded or on the power play simply because of a low overall number of shots against in the game.
I had a theory that one of the reasons that goalies often put up low save percentages when not facing very many shots was that they faced a higher percentage of power play shots. It turns out that the exact opposite was true, at least in 2009-10. One of the reasons that those teams took few shots in the first place was that they did not tend to have very many power play opportunities. The high shot teams had a situational distribution that is very similar to the overall average.
It seems apparent that save percentage has an impact on shots against. Teams that posted high shot totals tended to have very low shooting percentages early in the game, while the opposite is true for teams with low shot totals. There does appear to be some relationship between high shots against and a higher save percentage, although it is still somewhat uncertain how much that has to do with a potential shot quality effect and how much the shots against are caused by the high save percentage.
A very high shots against total tends to come in games where one team is significantly better than the other and where the better team has some incentive to keep playing for 60 minutes (i.e. the score is close or the team being outshot has the lead). That is usually only possible when the goalie on the weaker team is having a good day. After all, if the better team gets 3 or 4 goals and builds a comfortable lead then they usually shut it down somewhat and don't end up hitting the 40+ shot range.
It may be possible that goalies on weak teams get more chances to pad their stats with 40+ shots against games where a lot of the shots are of relatively low quality. It is possible that this counterbalances the likelihood that bad teams would tend to give up higher numbers of scoring chances against. I think more analysis needs to be done to determine whether there is an overall effect. All studies I've seen that look at seasonal averages for all teams show no relationship between save percentage and shots against, so I don't doubt that for most teams it all comes out even in the wash, but it remains to be seen whether there are unusual effects on outlying teams such as the Panthers or the Devils.
Thursday, January 21, 2010
Shutouts and Shots Against
Martin Brodeur is the all-time shutout leader in professional hockey, having surpassed both Terry Sawchuk's NHL record and George Hainsworth's professional record earlier this season. With his blanking of Florida last night Brodeur now sits at 108 for his career.
Holding the opposition off the scoresheet 108 times (and counting) is a terrific achievement. The vast, vast majority of hockey goalies who have ever played the game would not have achieved that mark even if placed in exactly the same situation with exactly the same opportunities, and most of them would likely not have come close.
However, it possible that there are a few who would have not only come close, but perhaps even surpassed Brodeur's mark. We'll never know for sure, because everyone is affected by situational factors and it's impossible to completely simulate any "what-if" scenario, but as with any record or achievement it is important to properly establish the context.
Shutouts depend on two variables: The quality of a goalie, and the quality of the team's defensive play. Defensive play can be split into two sections, the quantity of shots against and the quality of shots against. Evaluating shot quality is still a bit of a tricky issue but shot quantity is a simple matter of record, with the small caveat that there is good reason to believe that the counts are not completely consistent from rink to rink.
The goalie reference site HockeyGoalies.org has game-by-game breakdowns for every NHL goalie from 1985-86 to 2008-09. I chose to look at the period from 1993-94 to 2008-09, which encompasses essentially the entire career of Martin Brodeur. I chose for my sample all the goalies who rank on the current top 10 list for active leaders in career games played or career shutouts. To that group I added Hasek, Roy, Belfour, Joseph and Kolzig to make up a sample of 17 top-class netminders.
I looked at every game in which any of the goalies played at least 56 minutes and got the decision (win, loss, tie, or OT/SO loss). Here is a chart of the shutout frequency for the group. On the X-axis is the average number of shots per period, rounded off to the nearest one (e.g. 8 shots against per period means 23-25 shots against per game). The reason for grouping the shots in this manner was to increase the sample size for each data point on the chart. On the Y-axis is the percentages of games that ended in a shutout. The relationship between shots against and shutouts is very obvious. Facing fewer shots against helps a goalie record significantly more shutouts.
Having established that, we can move on to the individual breakdowns. Let's begin with my favourite comparison, Dominik Hasek vs. Martin Brodeur. Here are the number of times that each of them has faced a specific number of shots per period, and how many shutouts they have recorded in those chances.
2 shots/pd: Hasek 0/0, Brodeur 0/0
3 shots/pd: Hasek 0/1, Brodeur 1/2
4 shots/pd: Hasek 2/4, Brodeur 1/9
5 shots/pd: Hasek 5/19, Brodeur 7/37
6 shots/pd: Hasek 5/46, Brodeur 12/92
7 shots/pd: Hasek 13/69, Brodeur 19/156
8 shots/pd: Hasek 13/84, Brodeur 18/192
9 shots/pd: Hasek 7/85, Brodeur 23/171
10 shots/pd: Hasek 13/113, Brodeur 8/112
11 shots/pd: Hasek 12/89, Brodeur 5/72
12 shots/pd: Hasek 7/67, Brodeur 5/49
13 shots/pd: Hasek 2/30, Brodeur 2/30
14 shots/pd: Hasek 1/16, Brodeur 0/9
15 shots/pd: Hasek 0/10, Brodeur 0/2
16 shots/pd: Hasek 0/3, Brodeur 0/2
17 shots/pd: Hasek 0/3, Brodeur 0/0
18 shots/pd: Hasek 0/0, Brodeur 0/0
19 shots/pd: Hasek 0/1, Brodeur 0/0
On a percentage basis, Hasek has the better shutout percentage at 7 different shot levels while Brodeur has the edge 4 times. What is more noticeable is that the two goalies faced very different shot distributions. Brodeur's curve is centered around 8 while Hasek's chart peaks at 10. By multiplying the probabilities we can estimate that a typical goalie in the sample would be expected to record 53 shutouts facing Hasek's shots and 88 shutouts facing Brodeur's. That means on a relative basis Hasek was 51% better than the rest of the group compared to 15% for Brodeur.
The difference is further revealed when we take Hasek's rates and apply them to Brodeur's games, and vice versa. Hasek with Brodeur's shots against would be expected to record a whopping 125 shutouts. Brodeur with Hasek's shots against would be expected to end up with just 60.
To be fair to Brodeur, it isn't usually flattering to any goalie to be compared against the Dominator. Furthermore, there is some evidence that Brodeur prevents shots and that his home rink may have been a bit cheap in recording shots against. Let's give him the benefit of the doubt, and shift his rates by 1 shot/period (i.e. crediting him for 3 extra shots against per game). I'd say that's very probably overstating the effect, but I'll be conservative. That lowers the expected shutout numbers to 76, meaning that Brodeur outperforms by 33%. That's a solid mark, but still short of Hasek.
To make up the full difference, we would have to assume that Hasek was the opposite of Brodeur, that he creates an extra shot against per period. There is nothing at all to suggest an effect anywhere close to that large, but if Hasek's rates are shifted by 1 shot/period in the opposite direction we get the following:
Hasek: 80 shutouts, 62 expected, +29%
Brodeur: 101 shutouts, 76 expected, +33%
Even with an edge of up to six shots per game, Brodeur barely beats out Hasek. That's not taking into account the number of power play shots against and the quality of the defences in front of each goalie. Brodeur is the all-time shutout leader, but I think it's fair to say that there was at least one guy who was still clearly better at shutting out the other team.
Sample size is a potential issue with this analysis. For example, Roberto Luongo only had 3 games where he faced an average of 5 shots against per period or less, and he did not record a shutout in any of them. However that is far too few games to tell whether Luongo has any unusual performance patterns against that level of shots against.
It may be better to raise the sample size by consolidating the shot levels even further. The average shutout frequencies created some natural pairings, since as it turns out 6/7, 8/9, 10/11, and 12/13 all have shutout percentages within 1% of each other. I'll also include 4/5 as a grouping, since shutouts occurred 21% of the time with 4 shots per period and 17% of the time with 5. I excluded everything below 4 or above 13 because those events were so infrequent and therefore likely not useful for predictions. Here are the shutout results compared to expected for all the goalies in the sample, for that particular shot range only, ranked in order of performance above average:
Hasek: 79 SO, 51 exp, +55%
Luongo: 45 SO, 32 exp, +41%
Nabokov: 48 SO, 39 exp, +23%
Brodeur: 100 SO, 88 exp, +14%
Lalime: 35 SO, 32 exp, +9%
Roy: 46 SO, 43 exp, +7%
Belfour: 62 SO, 59 exp, +5%
Giguere: 32 SO, 31 exp, +3%
Kiprusoff: 30 SO, 29 exp, +3%
Turco: 36 SO, 38 exp, -5%
Vokoun: 29 SO, 32 exp, -9%
Joseph: 47 SO, 54 exp, -13%
Osgood: 48 SO, 57 exp, -16%
Khabibulin: 38 SO, 47 exp, -19%
Theodore: 27 SO, 34 exp, -21%
Roloson: 23 SO, 31 exp, -26%
Kolzig: 35 SO, 51 exp, -31%
"Average" as defined here really represents something well north of the true league average, since the only guys in this sample are top-flight goalies. That just makes Hasek and Luongo's numbers even more impressive. Factor in shot prevention and/or scorer bias and goalies like Belfour and Brodeur move up a bit as well. It's possible Brodeur should be in third place instead of Nabokov, all things considered. I think it's fair to say that Brodeur has demonstrated a very good shutout ability, and part of the reason that he doesn't have as many high-shot shutouts as other goalies is that his teammates were much less likely to give up that many shots against.
That's not too bad of a list in terms of the order, but it does seem that there are some team effects behind the numbers. Some teams are probably more likely to create easy shutouts for their goalies. Compare, say, Patrick Lalime's numbers against Curtis Joseph's. In any event, this reinforces earlier work I've done on this topic that show Hasek and Luongo were terrific at recording shutouts. Keep in mind however that while shutouts contain some information they are still a bit of an arbitrary stat. There is certainly a lot more to goaltending than shutouts.
Holding the opposition off the scoresheet 108 times (and counting) is a terrific achievement. The vast, vast majority of hockey goalies who have ever played the game would not have achieved that mark even if placed in exactly the same situation with exactly the same opportunities, and most of them would likely not have come close.
However, it possible that there are a few who would have not only come close, but perhaps even surpassed Brodeur's mark. We'll never know for sure, because everyone is affected by situational factors and it's impossible to completely simulate any "what-if" scenario, but as with any record or achievement it is important to properly establish the context.
Shutouts depend on two variables: The quality of a goalie, and the quality of the team's defensive play. Defensive play can be split into two sections, the quantity of shots against and the quality of shots against. Evaluating shot quality is still a bit of a tricky issue but shot quantity is a simple matter of record, with the small caveat that there is good reason to believe that the counts are not completely consistent from rink to rink.
The goalie reference site HockeyGoalies.org has game-by-game breakdowns for every NHL goalie from 1985-86 to 2008-09. I chose to look at the period from 1993-94 to 2008-09, which encompasses essentially the entire career of Martin Brodeur. I chose for my sample all the goalies who rank on the current top 10 list for active leaders in career games played or career shutouts. To that group I added Hasek, Roy, Belfour, Joseph and Kolzig to make up a sample of 17 top-class netminders.
I looked at every game in which any of the goalies played at least 56 minutes and got the decision (win, loss, tie, or OT/SO loss). Here is a chart of the shutout frequency for the group. On the X-axis is the average number of shots per period, rounded off to the nearest one (e.g. 8 shots against per period means 23-25 shots against per game). The reason for grouping the shots in this manner was to increase the sample size for each data point on the chart. On the Y-axis is the percentages of games that ended in a shutout. The relationship between shots against and shutouts is very obvious. Facing fewer shots against helps a goalie record significantly more shutouts.
Having established that, we can move on to the individual breakdowns. Let's begin with my favourite comparison, Dominik Hasek vs. Martin Brodeur. Here are the number of times that each of them has faced a specific number of shots per period, and how many shutouts they have recorded in those chances.
2 shots/pd: Hasek 0/0, Brodeur 0/0
3 shots/pd: Hasek 0/1, Brodeur 1/2
4 shots/pd: Hasek 2/4, Brodeur 1/9
5 shots/pd: Hasek 5/19, Brodeur 7/37
6 shots/pd: Hasek 5/46, Brodeur 12/92
7 shots/pd: Hasek 13/69, Brodeur 19/156
8 shots/pd: Hasek 13/84, Brodeur 18/192
9 shots/pd: Hasek 7/85, Brodeur 23/171
10 shots/pd: Hasek 13/113, Brodeur 8/112
11 shots/pd: Hasek 12/89, Brodeur 5/72
12 shots/pd: Hasek 7/67, Brodeur 5/49
13 shots/pd: Hasek 2/30, Brodeur 2/30
14 shots/pd: Hasek 1/16, Brodeur 0/9
15 shots/pd: Hasek 0/10, Brodeur 0/2
16 shots/pd: Hasek 0/3, Brodeur 0/2
17 shots/pd: Hasek 0/3, Brodeur 0/0
18 shots/pd: Hasek 0/0, Brodeur 0/0
19 shots/pd: Hasek 0/1, Brodeur 0/0
On a percentage basis, Hasek has the better shutout percentage at 7 different shot levels while Brodeur has the edge 4 times. What is more noticeable is that the two goalies faced very different shot distributions. Brodeur's curve is centered around 8 while Hasek's chart peaks at 10. By multiplying the probabilities we can estimate that a typical goalie in the sample would be expected to record 53 shutouts facing Hasek's shots and 88 shutouts facing Brodeur's. That means on a relative basis Hasek was 51% better than the rest of the group compared to 15% for Brodeur.
The difference is further revealed when we take Hasek's rates and apply them to Brodeur's games, and vice versa. Hasek with Brodeur's shots against would be expected to record a whopping 125 shutouts. Brodeur with Hasek's shots against would be expected to end up with just 60.
To be fair to Brodeur, it isn't usually flattering to any goalie to be compared against the Dominator. Furthermore, there is some evidence that Brodeur prevents shots and that his home rink may have been a bit cheap in recording shots against. Let's give him the benefit of the doubt, and shift his rates by 1 shot/period (i.e. crediting him for 3 extra shots against per game). I'd say that's very probably overstating the effect, but I'll be conservative. That lowers the expected shutout numbers to 76, meaning that Brodeur outperforms by 33%. That's a solid mark, but still short of Hasek.
To make up the full difference, we would have to assume that Hasek was the opposite of Brodeur, that he creates an extra shot against per period. There is nothing at all to suggest an effect anywhere close to that large, but if Hasek's rates are shifted by 1 shot/period in the opposite direction we get the following:
Hasek: 80 shutouts, 62 expected, +29%
Brodeur: 101 shutouts, 76 expected, +33%
Even with an edge of up to six shots per game, Brodeur barely beats out Hasek. That's not taking into account the number of power play shots against and the quality of the defences in front of each goalie. Brodeur is the all-time shutout leader, but I think it's fair to say that there was at least one guy who was still clearly better at shutting out the other team.
Sample size is a potential issue with this analysis. For example, Roberto Luongo only had 3 games where he faced an average of 5 shots against per period or less, and he did not record a shutout in any of them. However that is far too few games to tell whether Luongo has any unusual performance patterns against that level of shots against.
It may be better to raise the sample size by consolidating the shot levels even further. The average shutout frequencies created some natural pairings, since as it turns out 6/7, 8/9, 10/11, and 12/13 all have shutout percentages within 1% of each other. I'll also include 4/5 as a grouping, since shutouts occurred 21% of the time with 4 shots per period and 17% of the time with 5. I excluded everything below 4 or above 13 because those events were so infrequent and therefore likely not useful for predictions. Here are the shutout results compared to expected for all the goalies in the sample, for that particular shot range only, ranked in order of performance above average:
Hasek: 79 SO, 51 exp, +55%
Luongo: 45 SO, 32 exp, +41%
Nabokov: 48 SO, 39 exp, +23%
Brodeur: 100 SO, 88 exp, +14%
Lalime: 35 SO, 32 exp, +9%
Roy: 46 SO, 43 exp, +7%
Belfour: 62 SO, 59 exp, +5%
Giguere: 32 SO, 31 exp, +3%
Kiprusoff: 30 SO, 29 exp, +3%
Turco: 36 SO, 38 exp, -5%
Vokoun: 29 SO, 32 exp, -9%
Joseph: 47 SO, 54 exp, -13%
Osgood: 48 SO, 57 exp, -16%
Khabibulin: 38 SO, 47 exp, -19%
Theodore: 27 SO, 34 exp, -21%
Roloson: 23 SO, 31 exp, -26%
Kolzig: 35 SO, 51 exp, -31%
"Average" as defined here really represents something well north of the true league average, since the only guys in this sample are top-flight goalies. That just makes Hasek and Luongo's numbers even more impressive. Factor in shot prevention and/or scorer bias and goalies like Belfour and Brodeur move up a bit as well. It's possible Brodeur should be in third place instead of Nabokov, all things considered. I think it's fair to say that Brodeur has demonstrated a very good shutout ability, and part of the reason that he doesn't have as many high-shot shutouts as other goalies is that his teammates were much less likely to give up that many shots against.
That's not too bad of a list in terms of the order, but it does seem that there are some team effects behind the numbers. Some teams are probably more likely to create easy shutouts for their goalies. Compare, say, Patrick Lalime's numbers against Curtis Joseph's. In any event, this reinforces earlier work I've done on this topic that show Hasek and Luongo were terrific at recording shutouts. Keep in mind however that while shutouts contain some information they are still a bit of an arbitrary stat. There is certainly a lot more to goaltending than shutouts.
Friday, January 8, 2010
Puck Prospectus: The Best Goalie in 2009
Here's a link to my Puck Prospectus article on the best goalie in the calendar year of 2009. Spoiler alert: It's the guy I said wasn't worth his contract in this post from the summer of 2008. Whoops. Actually, in my defence, I said that he had to improve on his play to be able to justify his paycheque, which I think was probably a true statement at the time, and Miller certainly appears to have done that over the last 12 months.
I just wanted to throw in a few comments about the Sabres and shot quality here, since they are relevant to Miller's performance. The debate continues over the significance of shot quality measures and as such I think it's a topic that is worth investigating. I'd say that the immediate post-lockout Sabres are one of the most interesting case studies for shot quality analysis, because there seems to be a discrepancy between what one would intuitively expect and what the shot quality metrics claim. The shot data says the Sabres have tended to allow easier than average shots against, but with the offensive style that Buffalo played up until this season I think the general perception was that Miller was often being hung out to dry.
I wonder if a higher percentage of shots and goals against came on the rush for the Sabres in those seasons. The team was certainly shooting the lights out themselves, which indicates that they were creating some pretty good chances, and several of their players reached scoring levels that they hadn't reached before and haven't matched since. That suggests some kind of team effect, and it seems reasonable to me that a high-event team would see the percentages go up at both ends of the ice, just like a conservative low-event team would likely make the job easier for their own goalie in exchange for creating less offence at the good end of the rink.
I also suspect that Buffalo didn't play much to the score defensively, especially at home, and kept pushing for goals. From 2005-06 to 2007-08, the Sabres scored 3.67 goals per game at home and allowed 2.84 against. On the road, they scored 3.04 and allowed 2.89. That's a 21% scoring jump at home with almost an identical defensive record. Compare that to an average team, which scores 11% more at home and allows 11% fewer goals against. In 2006-07 the Sabres won the President's Trophy while allowing the fourth-most third period goals against of any team in the league. To put that into context, the last two President's Trophy winners both allowed the fewest third period goals against in the league. At the same time, the Sabres were also shooting the lights out late in the game, as from 2005-06 to 2007-08, Buffalo's lowest rank in third period goals scored was 4th.
This year Buffalo is tied for third in fewest goals against in the third period. Buffalo's third period goal distribution (+41/-29) is in fact identical to that of the New Jersey Devils. Without knowing the shot totals it is tough to say how much the goaltending has to do with that, but that's quite uncharacteristic for post-lockout Buffalo. Over the past three seasons the most similar team to the Sabres in third period scoring has been the Carolina Hurricanes, not exactly a team that anyone would confuse with the Devils. The Sabres are also 17-0-0 when leading after two periods in 2009-10, which is quite an improvement given that closing out games is something that the team has been pretty mediocre at over the last three seasons.
Perhaps there is a shot quality effect that isn't being accounted for in terms of rush chances. Time and space affects shot quality, both in terms of allowing the shooter to make a better shot as well as giving him more available options for the defensive team and goalie to worry about and try to defend against. We know that power play shots are more likely to go in than even strength shots from the exact same spot on the ice. That is likely because the shooter has more time and space to make their shot, and that the power play team can use quick puck movement to create a more difficult scoring chance for the goalie. Those same factors are why odd-man rushes are also dangerous scoring chances.
It wouldn't be possible to identify every rush chance from the play-by-play records, but I wonder if goalies see their save percentages drop if they face a shot against within, say, 8 seconds of a shot at the other end of the rink (adjusted for scoring location, of course)?
I'd say that the statistical evidence suggests that Miller has improved his game lately from where he was a few seasons ago. He looks better to my eye this year as well. It remains possible that there were some team factors that exaggerated his apparent recent jump from good to great. I would welcome the input of any Sabres fans if they have any additional insights on the post-lockout Sabres' play, shot quality, and its possible impact on Ryan Miller.
I just wanted to throw in a few comments about the Sabres and shot quality here, since they are relevant to Miller's performance. The debate continues over the significance of shot quality measures and as such I think it's a topic that is worth investigating. I'd say that the immediate post-lockout Sabres are one of the most interesting case studies for shot quality analysis, because there seems to be a discrepancy between what one would intuitively expect and what the shot quality metrics claim. The shot data says the Sabres have tended to allow easier than average shots against, but with the offensive style that Buffalo played up until this season I think the general perception was that Miller was often being hung out to dry.
I wonder if a higher percentage of shots and goals against came on the rush for the Sabres in those seasons. The team was certainly shooting the lights out themselves, which indicates that they were creating some pretty good chances, and several of their players reached scoring levels that they hadn't reached before and haven't matched since. That suggests some kind of team effect, and it seems reasonable to me that a high-event team would see the percentages go up at both ends of the ice, just like a conservative low-event team would likely make the job easier for their own goalie in exchange for creating less offence at the good end of the rink.
I also suspect that Buffalo didn't play much to the score defensively, especially at home, and kept pushing for goals. From 2005-06 to 2007-08, the Sabres scored 3.67 goals per game at home and allowed 2.84 against. On the road, they scored 3.04 and allowed 2.89. That's a 21% scoring jump at home with almost an identical defensive record. Compare that to an average team, which scores 11% more at home and allows 11% fewer goals against. In 2006-07 the Sabres won the President's Trophy while allowing the fourth-most third period goals against of any team in the league. To put that into context, the last two President's Trophy winners both allowed the fewest third period goals against in the league. At the same time, the Sabres were also shooting the lights out late in the game, as from 2005-06 to 2007-08, Buffalo's lowest rank in third period goals scored was 4th.
This year Buffalo is tied for third in fewest goals against in the third period. Buffalo's third period goal distribution (+41/-29) is in fact identical to that of the New Jersey Devils. Without knowing the shot totals it is tough to say how much the goaltending has to do with that, but that's quite uncharacteristic for post-lockout Buffalo. Over the past three seasons the most similar team to the Sabres in third period scoring has been the Carolina Hurricanes, not exactly a team that anyone would confuse with the Devils. The Sabres are also 17-0-0 when leading after two periods in 2009-10, which is quite an improvement given that closing out games is something that the team has been pretty mediocre at over the last three seasons.
Perhaps there is a shot quality effect that isn't being accounted for in terms of rush chances. Time and space affects shot quality, both in terms of allowing the shooter to make a better shot as well as giving him more available options for the defensive team and goalie to worry about and try to defend against. We know that power play shots are more likely to go in than even strength shots from the exact same spot on the ice. That is likely because the shooter has more time and space to make their shot, and that the power play team can use quick puck movement to create a more difficult scoring chance for the goalie. Those same factors are why odd-man rushes are also dangerous scoring chances.
It wouldn't be possible to identify every rush chance from the play-by-play records, but I wonder if goalies see their save percentages drop if they face a shot against within, say, 8 seconds of a shot at the other end of the rink (adjusted for scoring location, of course)?
I'd say that the statistical evidence suggests that Miller has improved his game lately from where he was a few seasons ago. He looks better to my eye this year as well. It remains possible that there were some team factors that exaggerated his apparent recent jump from good to great. I would welcome the input of any Sabres fans if they have any additional insights on the post-lockout Sabres' play, shot quality, and its possible impact on Ryan Miller.
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