Monday, April 27, 2009

2008-09 Shot Quality

Behind the Net has posted shot quality data for goalies in 2008-09. I am particularly interested in these numbers, as they are based on the same ESPN data I am collecting for the playoffs. As I have been discussing lately there is still room for improvement with these kind of metrics, but they are better than the raw data and at least provide some evidence of the actual level of performance of NHL goalies.

With the Vezina finalists due to be announced today, I had more or less settled on Tim Thomas, Tomas Vokoun and Roberto Luongo as my top 3, and this is pretty good evidence for that viewpoint. All three of them were terrific at even-strength this year. My pick for the most underrated goalie in the league, Kari Lehtonen, also does very well. Henrik Lundqvist ranks highly, although I'm not sure whether we can trust his numbers or not as Madison Square Garden's reporting biases are well-known.

Evgeni Nabokov, Miikka Kiprusoff, and Niklas Backstrom don't look all that good after adjusting for shot quality. Both Nabokov and Kiprusoff have about average shot quality against, so they have little excuse for their relatively unimpressive save percentages, and Backstrom faced the easiest shots against in the league.

Cam Ward and Steve Mason are two others who could get some voting support. They wouldn't be bad choices, and would both be preferable to any of the above three, but I don't think they would be the best picks either.

Regardless, the voting results for this year's Vezina Trophy and First Team All-Star goalie should be very interesting and will show us what the GMs and the media value in evaluating goalies.

Saturday, April 25, 2009

Shooting High

I am tracking shots based on ESPN's shot charts for the playoffs, but I have also been regularly checking out CBS Sportsline's shot charts because they add another interesting piece of information: Where the shot was targeted on net. For each shot they record one of five target zones: High glove, high blocker, low glove, low blocker, or 5-hole.

I haven't compiled any numbers other than for this year's playoffs, but Hockey Numbers did a post a while back that gives the CBS data broken down by shot location for the 2006-07 season. There seemed to be a lot of shots missing in that sample as the average save percentage was much lower than the official NHL numbers, but the results still conclusively prove what all hockey players know: That shooters are much more likely to score if they shoot high.

It doesn't seem to matter much where a shot is targeted on net from right to left (e.g. high glove or high blocker are about the same), the key difference is whether the shot is high or low. There are of course some goalies who are better on the blocker side or on the glove side, and all goalies probably have slightly less success on five-hole shots than shots that are low to either side, but those differences are small compared to the difference between top shelf and along the ice.

The 2006-07 data has a save percentage difference of .054 between high shots and low shots. This year in the playoffs, there has been a .942 save percentage on low shots and an .872 save percentage on high shots, for an even more extreme gap of .070. Those differences make a pretty good case that shot height should be included in measurements of shot quality.

As is unfortunately often the case with real-time stats, however, the CBS reporting system is pretty suspect. They seem to have fixed the earlier problem of missing shots, but there are large variances in high shot frequency from rink to rink. Here are the stats by series:

BOS vs. MTL: .917 low, .857 high, 27% high shots
WSH vs. NYR: .946 low, .868 high, 19% high shots
NJD vs. CAR: .961 low, .907 high, 41% high shots
PIT vs. PHI: .961 low, .800 high, 14% high shots
SJS vs. ANA: .926 low, .933 high, 19% high shots
DET vs. CBJ: .919 low, .840 high, 20% high shots
VAN vs. STL: .961 low, .875 high, 16% high shots
CHI vs. CGY: .928 low, .845 high, 35% high shots

We would expect high shots to be correlated with space on the ice. The more time and space a shooter has, the more likely he is going to be able to shoot high. I wouldn't be surprised that a tight-checking series like Vancouver/St. Louis might have a below-average amount of high shots. However, even in that particular series the number of actual high shots is almost certainly understated. In game 4 in St. Louis every single one of Roberto Luongo's 49 shots against were recorded as being low shots, which is extraordinarily unlikely and seems to be merely a case of an indifferent scorekeeper. I observed several other similar games where all or nearly all of the shots were booked as low shots.

The scorers in New Jersey and Carolina appear to be the opposite, booking too many shots as high. The high shot rate in that series is almost double that of all the other series combined, and the save percentage against high shots is much higher than average. The Calgary series also has an abnormal ratio, but the save percentage on high shots is just .845. Either the shooters are really managing to go upstairs that often, or else Kiprusoff and Khabibulin are doing a very poor job of handling high shots.

In most series both goalies have faced a pretty similar number of high shots. One series stood out by having a large gap between the teams, Detroit's 4 game sweep of Columbus. Based on shot distances and shot locations, it looks like Columbus allowed easier shot quality against than Detroit. Over half (54%) of the shots against Steve Mason came from the point or were perimeter shots, while the same areas accounted for just 37% of the shots against Chris Osgood. As a result, Detroit's outshooting advantage is counterbalanced by a longer than average shot distance. I have Detroit with an expected goals figure just 0.3 ahead of Columbus for the series. That is similar to the shot quality results at Hockey Numbers (Detroit +0.5).

When we consider where the shots were targeted, it becomes a different story. The rate of high shots against Steve Mason was twice as high as the rate against Chris Osgood (26% to 13%). If we adjust only based on the average save percentages for low and high shots, that means we would expect Osgood to have the easier job with a .933 expected save percentage compared to .924 for Mason. If we recalculate the expected goals based on those save percentages, Detroit would have been expected to score 3.4 more goals than Columbus over the 4 game series.

What seems possible is that even though Columbus' shooters were getting into good shooting locations, they were mostly shooting under pressure from defenders. In contrast, Detroit was setting up more open shots, which allowed their shooters to snipe up high against Mason. I must confess I wasn't able to catch any of the games of that series, however, so if you did follow that series then feel free to comment on whether you believe the shot quality figures (both based on ice location and target location) seem correct.

If we adjust for both where the shots were coming from and where they were targeted, based on playoff averages so far, I estimate that Mason had a .933 expected save percentage while Osgood was at .922.

We can use those figures to conclude that the much-maligned Chris Osgood did surprisingly well in round 1, but it wasn't a very good playoff debut for Steve Mason. The stats suggest that the likely Calder Trophy winner had the worst overall performance of any goalie in the playoffs, although at least Jose Theodore ranks below him on a per-game basis.

I think it is pretty evident that shot quality would be improved if the target location of the shot was accurately tracked. By combining that information with where the shot was coming from on the ice, it should be possible to get a more accurate scoring probability. Unfortunately CBS Sportsline's tracking system seems to too untrustworthy to be useful at the moment. To evaluate all goalies on a level playing field it is necessary to standardize the reporting to remove or at least drastically reduce rink reporting bias.

Friday, April 24, 2009

Football, Hockey, and Player Development

Football Outsiders' Mike Tanier wrote an excellent article on drafting vs. player development (scroll down past the mock draft satirizing to get to the real meat of the post). He echoes my thoughts on the topic by pointing out that there are many post-draft variables that sculpt a player's future career success.

If that's true for 22 year old men with college degrees, then it is pretty likely to be even more true for 18 year old high school kids aspiring to play pro hockey.

And while we are comparing football to hockey, I thought of an interesting comparison: Brett Favre and Martin Brodeur. If career wins and shutouts trump all in the greatest of all-time debate, then doesn't holding the career wins and passing yards records make Brett Favre the greatest QB of all time?

Favre and Brodeur have more in common than holding their respective sports' career wins record. Both are distinguised first and foremost by durability, and have reputations for consistency. Neither has had any individual seasons that rank among the few greatest seasons ever - according to Aaron Schatz of Football Outsiders, Favre doesn't have a single season in the top 50 QB seasons ever, and he has just one in the top 80. Brodeur also has only a couple of seasons that rank among the best in save percentage compared to league average.

Despite this both of them have won some major awards, with 3 MVPs for Favre and 4 Vezinas for Brodeur. They also have experienced team success, with 3 Stanley Cup rings and 1 Super Bowl ring between them.

As the groundswell of support for Brodeur as a best-ever candidate continues to grow, it might be wise to keep in mind how Brett Favre is ranked. A collaborative ESPN effort to rank the all-time top 10 QBs from a year ago ranked Favre 8th, and even after his retirement there is still debate about whether Favre is a top-5 guy.

It should be said that your individual evaluative criteria come into play when evaluating athletes who were distinguished more by durability and longevity than by peak play, like Brodeur and Favre were. However, it's just something to think about before automatically declaring the goalie with the most wins and shutouts to be the greatest ever.

Tuesday, April 21, 2009

The Value of Rebound Control

Dirk Hoag, who runs the excellent stats-focused blog On the Forecheck, has been measuring rebound shots from the NHL play-by-play logs over the last few years and was kind enough to provide me with a summary of rebound shots against by team for this season to date. I was particularly interested in this year's numbers since Martin Brodeur's absence should give us an idea of the impact of a goalie on rebounds against. You can't go very far on a New Jersey Devils blog or message board without running across someone either praising Brodeur's rebound control or trashing Scott Clemmensen's, so I think it is fair to say that one of the best at the skill was replaced for 40 games by one of the worst. Not to mention, Brodeur himself seems to think that rebound control is a pretty important skill. What was the difference for New Jersey in the mostly Marty-less 2008-09?

First, we need some context. The Forechecker has posted data online from each of the past several seasons (for example, here is a post from last March for the 2007-08 season). These data sets aren't usually complete, but they give us a pretty good sample to work with. Over the last three seasons, with Brodeur nearly always in net, The Forechecker has estimated the Devils as averaging 1.5, 1.4, and 1.4 rebound shots against per game. That is compared to a league average of just below 1.6, and is a good enough to rank 7th best in the league over that time period.

New Jersey Devils, 2008-09: 1.22 rebound shots against per game, 4th fewest in the NHL

According to the NHL play-by-play data, New Jersey took out one of the best rebound controlling goalies in the league and put in one of the worst, and not only improved their numbers from previous years but ended up among the league leaders in fewest rebound shots against.

How is this possible? Based on this result and other evidence, I think rebound control is an overrated skill. That is not to say it is unimportant, just that it gets overly emphasized in terms of its impact on goals against. This is for the same reason that most non-save goalie skills are overrated: Because the rest of the team can compensate for it. Clemmensen's teammates knew there were going to rebounds when he was in net, and they made sure the other team didn't get them. This shift happened without any apparent effect on the overall play - the Devils' rate of goals for, goals against, and shots against is very similar with Clemmensen and Brodeur in the net this season.

Rebound control is especially prone to being overemphasized because it is an obvious skill. You don't have to know much about goaltending technique to know whether a goalie is controlling his rebounds, you just need to watch where the puck ends up after it hits him. Lots of people who aren't goalies can speak knowledgeably about a goalie's rebound control. The problem comes when they focus too much on where the puck goes after a shot and not enough on whether or not it went in the net to begin with. A goalie who stops a high percentage of shots but has a tendency to allow awkward rebounds (someone like Tim Thomas, for example) will be consistently underrated by people who rely on subjective evaluation.

Despite the focus on rebounds, there really aren't that many rebound shots per game. This season there have been just 1.43 rebound shots against per team per game. Not only are the totals low, but there is not a whole lot of difference between teams in rebounds allowed. Over the last 4 seasons from The Forechecker's numbers, Detroit allowed the fewest rebound shots (1.25 per game) while Florida allowed the most (2.00 per game). That is not particularly surprising, since Detroit allowed the fewest total shots (25.6) while Florida allowed the most (33.1). Note that the difference in overall shots (7.5) is 10 times as high as the difference in rebound shots (0.75). Clearly it would be a big mistake to attribute a difference in shots against between teams primarily to rebounds.

A better measure of rebound prevention is the percentage of shots against that are rebound shots. The best team in the league this year, Buffalo, has faced a rebound shot on just 3.6% of their shots against. The worst team in the league, Carolina, has seen a second chance opportunity on 6.1% of their shots. That is a gap of 2.5%, which is a typical gap between the best and the worst in any given season. Even if we assume that the entire difference is a result of goalie skill, for a team with 30 shots against that accounts for a difference of about 0.75 rebounds per game, which at a typical rebound scoring rate is somewhere around 0.18 goals per game. A difference of 0.18 goals per game is equivalent to a save percentage difference of .006. That is just for this season, where we would expect some more randomness in the results. Over the 4 year sample, the difference between the best and worst is just 1.7%.

That would be a poor assumption, however, because it doesn't into account team defence. A better defence will clear more rebounds, and a team that allows fewer dangerous scoring chances will make it easier for the goalie to control his rebounds. Here are the correlation coefficients between team shot quality against and rebound shots percentage:

2005-06: 0.39
2006-07: 0.09
2007-08: 0.42
2008-09: 0.30

That looks to be pretty good evidence of an underlying relationship. If we take that into account, then that .006 gap might shrink to .003 or .004, and that is between the best and the worst. That's not even taking into account how good the defence is at clearing rebounds. Once you include that in the equation, there likely isn't a whole lot of margin left.

Is it possible that there is some other effect of rebound control that I am not missing? I brought up the possibility some time ago that goalies with good rebound control might be deterring shots, since opponents will be less likely to shoot from bad angles if they don't think they will be rewarded with either a goal or a rebound. That effect, if it exists, would be difficult to quantify.

These numbers are also subject to the limitations of NHL play-by-play data. If there is good reason to believe that more rebound shots and goals are taking place than are being counted, then we might have revise the strength of some of these conclusions.

One thing that may be possible is that poor rebound control may be an indicator of a goalie who is not on his game. It would be interesting to see if goalies are more likely to allow goals in games where they allow multiple rebound shots against.

I am certainly not saying that goalies should ignore rebound control or not try to develop their skills in that area. Excellent rebound control is of course preferable to poor rebound control, and will help prevent goals against. One of the reasons that we don't see a lot of difference in things like rebound control at the NHL level is that goalies with particularly bad skills in that area would never make it there in the first place. However, we still need to be particularly careful to avoid making the mistake of letting the obvious nature of rebound control overly influence our evaluation of a goalie.

Wednesday, April 15, 2009

Shot Quality

ESPN's GameCast feature shows shot charts for every NHL game, which is quite useful to indicate the territorial play and to help evaluate goalie performance. I am a big fan of shot quality metrics like the one developed by Alan Ryder, but one of the limitations is that it reduces a team's shots against distribution to a single number. Even if we know that a team's shot quality against is 0.95, we don't know whether that is because they allow a lot of perimeter shots, or whether they are good at preventing in-close chances. I think this might be one of the reasons why some fans seem hesitant to trust the shot quality numbers.

As a result, I have developed my own system, using my typical brute-force approach. The objective is to achieve the dual goal of approximating scoring probabilities while also being able to qualitatively describe the type of chances a team gives up. Based on the scoring probability information given in this blog post from Behind the Net, I divided the rink up into 5 zones: Crease Area, Slot, Mid-Range, Point, and Perimeter. I used rink markings to divide the separate zones, which isn't exactly correct based on scoring percentages but becomes somewhat necessary for classifying chances. For the sake of time, everything is eyeballed except for chances from the crease area, which are defined as anything within 15 feet of the net inside the edges of the crease.

Here is the rink diagram:

The primary drawback of this technique is that it does not differentiate between power play and even-strength chances. I could split them out, but obviously it takes a bit of time to go through and count the chances so for now I'm lumping them all together. There are also certain rinks that seem to measure shot distances differently than everyone else (see this article by Alan Ryder), which means that it is not really fair to compare results directly between, say, goalies playing for the New York Rangers and goalies playing for the Tampa Bay Lightning. I'll have to work on some way to adjust for these discrepancies.

Just to be clear, I am not presenting this as an improvement on existing shot quality metrics. I hope the results will be similar, but I would certainly defer to other methods if there is a disagreement because they are much more precise in terms of identifying exact shot distance, shot type, etc. The primary reason for doing this is to get a better sense of the type of shots each goalie is facing. Is he facing a lot of shots from the perimeter? How well does his team cover the point shot? How many close-in chances does he face? And so on.

I don't have a large enough sample size to get high-confidence estimates of scoring likelihood from each area, but based on a sample from last year's playoffs the approximate average save percentages are:

Crease Area: .800
Slot: .850
Mid-Range: .925
Point: .960
Perimeter: .980

I'm planning to use this method to break down this year's playoff results, as well as to take a closer look at Martin Brodeur vs. his teammates in my continuing look at how goalies contribute to shots against. Criticisms and suggestions are welcome in the comments or via email.

Tuesday, April 14, 2009

The Replacements, Final Comparison

At season's end, the best backup comparison sample for Brodeur since 1993-94 ends with the following breakdown:

Brodeur: 19-9-3, 2.42, .916, 28.8 SA/60
Backups: 32-18-1, 2.40, .918, 29.3 SA/60

I'll just let those numbers speak for themselves. It's not a huge sample size, but there was no major effect on either GAA or shots against without Brodeur in the lineup. Nor, for that matter, was there much difference in New Jersey's goal scoring or winning percentage with or without the "best goalie in the NHL."

I think the "Brodeur saves 5+ shots per game" crowd has been permanently and decisively disproven by this season's results. For Marty to play that kind of sample size and to face just 0.5 shots per game fewer than his teammates is pretty good evidence that the range of shots against is fairly narrow. I do think that the "true" shots against differential between Brodeur and Clemmensen is likely more than 0.5 shots per game, as Brodeur happened to be the man in net during New Jersey's late season swoon, but the results certainly are in line with my estimate of +/- 1 shot per game on average as the goaltender's effect.

I think there is a substantial difference between Brodeur and Clemmensen in skills like rebound control and puckhandling. However, there is not much of a net effect on the team as a whole because the rest of the skaters adjust their play at least somewhat to the particular goaltender. That explains why we don't usually see much of an impact in the shots against and GAA data from goalie to goalie.

I'm not going to go much farther than that in terms of assigning significance to these results. Brodeur is a better goalie than Scott Clemmensen or Kevin Weekes. The numbers may have been similar, but Brodeur faced more difficult shot quality against and likely was affected to some degree by his long injury layoff. I suppose this season supports my overall position on Brodeur, but it is by no means the main piece of evidence in the argument. The results do show fairly plainly that New Jersey is an easy place to play goal, but that should have been obvious to begin with.

Thursday, April 9, 2009

How Not To Pick Vezina Winners

I sincerely hope that the general managers and sportswriters who vote on the end-of-season awards do not think like Rocky Bonanno.

His picks for Vezina nominees: Niklas Backstrom, Evgeni Nabokov, and Miikka Kiprusoff.

In my book that's going 0 for 3, as those three rank 15th, 19th, and 33rd respectively in the latest shot quality neutral save percentage rankings at Hockey Numbers. If you are going to just rank goalies entirely based on wins, at least put somebody like Cam Ward in there who actually has been having a good season.

And then there is this example of impeccable logic:

Honorable mention also goes to Boston's Tim Thomas, but 52 games played doesn't bring him up to snuff.

That's right, Thomas, you should have demanded your team play you more games. Don't you know that there is some magical point at around the 55 game mark that makes you instantly become worthy of Vezina consideration?

Take Evgeni Nabokov, for instance, who has played 59 games this season. It shouldn't even be necessary to explain why 59 games played is so much more valuable than 52, but I'll give it a try for all of you analysts out there who clearly don't understand goaltending.

Let's compare them through their first 52 games this season:

Nabokov: 36-8-7, 2.41, .911
Thomas: 34-11-7, 2.07, .933

Even though it looks like Thomas was by far the superior goaltender through the first 52 games, by playing more games Nabokov had a much harder workload. I mean, just look at the difference in the number of shots faced this year:

Shots against in 2008-09:
Evgeni Nabokov: 1,622
Tim Thomas: 1,621

Maybe Thomas would have let in his next shot, and then have his teammates score 33 own goals on him, dropping him behind Nabokov in save percentage. We just don't know, and that's why anything a goalie does in only 52 games is completely worthless.

Similarly, in his first 52 games this season Kiprusoff had fewer wins than Thomas did over the same span, as well as a 2.80 GAA and a .906 save percentage. In his extra games played over Thomas, Kipper has gone 12-8-1, 2.91, .895. To match Kiprusoff's season stats, Thomas would have only needed to win 11 out of his last 23 decisions, and put up a 4.78 GAA and an .805 save percentage.

Some of you might think that is pretty good evidence that Thomas has been a lot better than Kiprusoff. You would be wrong. Of course I do concede that the goalie currently leading the league in save percentage might not turn into by far the worst goalie in the history of the NHL over his next 23 games. That is possible, some might even say probable. But it could have happened. All we know is that Kiprusoff did play those extra games and Thomas didn't. Seventy-five is more than 52, and therefore Kipper has been a better goalie this season. End of story.

Wednesday, April 8, 2009

Steve Mason, Vezina Candidate?

Rookie Steve Mason has been getting a lot of awards attention this year. He is very likely to win the Calder Trophy, but there has also been some buzz about him being in the Vezina race as well, and I have even seen his name getting brought up in connection with the Hart Trophy.

Mason has some interesting splits stats that I think should be highlighted, and that may lead to some further discussion over whether he really deserves those accolades or not. For one thing, Mason has not been very consistent at all. The main reason for his excellent season is that he was absolutely lights-out in December (7-5-0, 1.41, .950, 3 SO). Since January 1, however, he has slowed considerably. The team has still been winning with him in net (20-11-6), but Mason's other numbers have been fairly ordinary in the New Year: .908 and 2.51.

Mason has 10 shutouts, but to counterbalance that he has allowed 4 goals or more 12 times, and he also has had a sub-.900 save percentage in 23 out of 58 starts.

Mason also has a very mediocre record against his own conference. Against Western Conference opponents he is 20-17-6, 2.58, .905. If you are familiar with his overall record, you can put two and two together and figure out that means he must have absolutely crushed the Eastern Conference, and you would be right about that to the tune of 12-1-1, 1.12. ,959.

One other surprising thing is Mason's shot quality against this season. Many people have pointed out Pascal Leclaire's 9 shutouts last season and Ken Hitchcock's typically strong defensive coaching and suggested that was the primary reason for Mason's numbers. The data suggest this is actually not the case. Columbus has allowed more difficult than average shot quality against this season. I looked in some more detail at the shots Mason faced during his December run and they didn't look to be any easier than normal. I don't think it is fair to say that Ken Hitchcock created Steve Mason. I think a better explanation is that Mason just rode a hot streak and played well over his head for about a month and a half before dropping down to a more typical level of play for a rookie goaltender.

As a matter of fact, from quickly looking at some past Hitchcock teams it looks like a lot of the great defensive play of his teams is a result of shot prevention, rather than a very easy shot quality against. That has held true this year, as the Blue Jackets have allowed the 4th fewest shots against per game this season. As a result, we would expect a Hitchcock goalie to have a lot of shutouts, but not necessarily a high save percentage.

Steve Mason was very, very good in the month of December. However, I'm not sure that one extremely good month, 2 decent months and 2 mediocre months makes you the best goalie over an 82 game season. Based on cumulative performance, though, Mason probably wouldn't be out of place in the top 5.

I don't think the Calder Trophy should be a slam dunk either. It is pretty much a dead heat between Mason and Nashville's Pekka Rinne. They have very similar statistics, including shot quality neutral stats. Nashville has done relatively better with Rinne in net (2.28 GAA, .652 win % vs. 2.93 GAA, .394 win % for backups) than Columbus has with Mason (2.22 GAA, .623 win % vs. 3.36 GAA, .432 win % for backups), although both of them have way outperformed their teammates. Mason has played more games, but games played as a rookie depends on a lot of factors other than goalie skill, first and foremost being the talent and health of whoever's job they had to steal. I'm pretty sure Mason will win it, but Rinne certainly wouldn't be a bad choice.

Sunday, April 5, 2009

Estimating 1970s Save Percentages

There has been a lot of work done in putting together hockey box scores, led by the Hockey Summary Project, which has enabled us to look at save percentage numbers for many past seasons. There are complete save percentage records available for the original six period from 1955 to 1967, and official save percentages are available since 1982. The period in the middle, however, is lacking, which makes it difficult to evaluate those particular goalies, including Hall of Famers like Dryden, Esposito, Giacomin, Cheevers, and Parent.

I do have playoff save percentages for every season in that period, so I had the idea of comparing how many shots against each goalie faced compared to league average in the playoffs, and using that number to estimate regular season shots against totals. From there, since we know the actual historical GAA, we can estimate save percentages for the seasons that are missing and thereby arrive at an estimated career save percentage for each goalie.

I tested this out, and it seemed to work well for goalies who consistently qualified for the playoffs, especially those who played on the same team. For example, it estimated Martin Brodeur to have a .913 career save percentage, and he is actually at .914. From the work of one dedicated Flyers fan, the one who is hosting the Hockey Summary Project, we have Bernie Parent's complete stats as a Flyer. His career save percentage in Philadelphia was .917. My estimated save percentage? The same .917.

These numbers probably make the method seem more accurate than it is, but I think the numbers are probably fairly reasonable. The system does not work well for some goalies, mainly those who had a number of seasons where they missed the playoffs or had a few deep playoff runs with one team but played the majority of their careers somewhere else. An example is Gilles Meloche, who played eleven seasons in the non-save percentage era and only made the playoffs in two of them. His non-playoff teams would have been very likely to give up more shots against than his playoff teams did, so his save percentage is probably understated. Roger Crozier is another guy whose results aren't that meaningful, since he played most of his career on bad teams but had a couple of deep playoff runs on good teams which make up the majority of his postseason participation.

Here is the complete list of goalies who faced at least 10,000 (estimated) shots against, sorted by goals over league average:

B. Smith.894.88319,142210.658.8269.4
D. Edwards.890.87913,124144.4-3.0141.4
D. Bouchard.889.88318,552111.3-3.8107.5
G. Smith.900.89916,69016.7-1.914.8

The lack of parity in the 1970s means that there is a lot of team effect included in these results. All of the guys in the top 5 played on very good teams, and their backups also did well by this measure. That's not to say they weren't good goalies, but of course they played in ideal situations.

I think Rogie Vachon, Mike Palmateer, and Dan Bouchard do pretty well here considering their teammates. If Billy Smith faced 5% easier shot quality than those guys, for example, he would be behind all three of them in career regular season goals above average. That seems very plausible to me, especially when you take into account how well Resch did in New York. On the other hand, Dryden would have needed to face 25% easier shot quality than Vachon to end up at the same level, and it is unlikely that Habs were anywhere near that good. The evidence suggests that Dryden was an example of a great goalie on a great team.

For guys like Gary Smith and Gilles Meloche just to show up at average is a strong result, since I highly doubt the California Golden Seals allowed league average shot quality against. I bet both of them were better than someone like Doug Favell, despite the 100+ goal gap between them. If Smith and Meloche faced shots that were 5% harder than average, they would rank up around the same level as Bouchard, Palmateer and Vachon.

To estimate the difference in save percentage from the best teams to the worst, we can look at the save percentages we do have. There are save percentages available from the 1970-71 season, for example, the fourth season after expansion, which gives some time for player movement between teams as well as a few years for the expansion teams to start recruiting and developing talent. The average save percentage for goalies on Original Six teams: .911. Average save percentage for goalies on expansion teams: .898. Even if we assume that the O6 goalies were 10% better than the goalies on expansion teams, which is almost certainly well overdoing it, that implies that the shot quality against was 5% easier in Toronto, Montreal, Boston, New York, Detroit and Chicago. I'd bet the true shot quality difference in those early years was probably closer to 10%.

I'm still not sure exactly how to rank Tony Esposito. His numbers are very good, at or near the top in every scenario, and yet I still feel that he was only the 3rd best goalie of his generation. Esposito is similar to Martin Brodeur in terms of playing a lot of games every year behind a mostly good defence.

The two guys who appear to have some explaining to do are Hall of Famers Gerry Cheevers and Ed Giacomin. How does Cheevers end up exactly at league average in save percentage in both the regular season and the playoffs if he was such a great goalie? And presumably Hall of Famers should not be below average in the regular season and dreadful in the playoffs like Giacomin was? I think Cheevers is in the Hall of Fame because of Bobby Orr and because Gilles Gilbert's bad playoff play made Cheevers look clutch, while Giacomin is in the Hall of Fame because of the New York media and fortunate timing (playing on an original six team right after expansion he grabbed a couple of First Team All-Star awards before the emergence of Dryden and Parent).

I think evaluating goalie play in the 1970s is all about figuring out the appropriate team adjustments, because there was so little parity around the league. It is pretty clear that Esposito, Parent and Dryden were the three best goalies of the decade (they also ranked 1-2-3 in my measure of GAA vs. backup goalies). I think it is still unclear who was the best of the next tier of starters. It's not fair to simply give that credit to whoever happened to play in Philadelphia or Long Island. I think there were a number of overlooked goalies in the next tier of solid starters who simply never had the fortune of playing with talented teammates (Meloche, Palmateer, Bouchard, Gary Smith, etc.).

When we are finally able to put together the complete save percentage record, it will be interesting to compare these estimates and hopefully break down team effects in a little more detail so we can figure out who comes next after the big 3 in the ranking of best goalies of the 1970s.

Thursday, April 2, 2009

The Emergence of Cam Ward

The development of young goalies is not usually a linear process. There are very few goalies who are very good almost right from day one. Even if goalies play well in their rookie seasons, they usually have to struggle through some ups and downs, like Carey Price is experiencing this year in Montreal. Sometimes goalie have a few rough seasons early in their careers, and then suddenly make the jump from mediocre to good (e.g. Marc-Andre Fleury last season). Other factors that can hinder development are bad teammates or injuries (and sometimes both, as in the case of Kari Lehtonen).

Cam Ward has the same birth year as Fleury and the same draft year as Lehtonen. He has had a bit of a different career path than those two guys, bursting onto the scene in spectacular fashion in 2006 when he won the starting job for Carolina in the playoffs and played so well he won the Conn Smythe Trophy. However, until this season he had never been able to replicate that level of play in the regular season and was clearly not playing at the same level as his two main peers.

Ward's playoff performance looks like a fluke when compared to his regular season results before and after, and maybe it was. It would be a mistake, however, to write Ward off as a one-shot wonder, even if he somehow caught lightning in a bottle back in 2006. The reason is that Cam Ward has one of the most straight-line development curves I have seen for a young goalie:

2005-06: 3.68, .882
2006-07: 2.93, .897
2007-08: 2.75, .904
2008-09: 2.45, .916

Ward just turned 25, and this is the year he has taken the leap to becoming an above-average goalie. His save percentage is very strong considering Carolina usually does not do a great job preventing dangerous scoring chances - Hockey Numbers has Ward in the top 10 among starting goalies this year in shot-quality neutral save percentage. He has solidly outplayed his backups over the last two seasons - 0.8 goals per game better last year, 0.5 goals per game this year, and Carolina has a much better winning percentage with Ward in net than without him over each of the last three seasons.

It is possible that Ward is simply having a strong year. However, his past results do support an above-average NHL career: Ward was a first round pick, he was the 2003-04 CHL goalie of the year, and in 2004-05 he put up a .937 save percentage in the AHL as a 20-year old. I was a bit skeptical of those results throughout Ward's early NHL career, as his junior and AHL teams were very strong defensively, but .937 is pretty strong even on a top defensive team and Ward has cemented his status as a legitimate NHL goalie with his continued development at the highest level.

Ward likely has even more room to develop, and I'd say right now he is on par with or maybe even a bit ahead of Fleury and not too far behind Lehtonen as the best goalie drafted in 2002 or 2003. Ward has also been a major contributor to the Hurricanes' postseason drive this season, and with just 5 games remaining it looks pretty likely that he is going to be returning to the playoffs for the first time since he skated around the RBC Center with the Stanley Cup in 2006. Ward is a much better goalie now than he was then, but time will tell if he can recapture the same postseason magic.