Saturday, December 31, 2011

Good Enough to Win

One thing that is often discussed about goalies by hockey fans is whether they are "good enough" to win a Stanley Cup. This is usually based on things like gut feel and extrapolating huge amounts of significance from small sample sizes; I have rarely seen anyone try to quantify what good enough to win a Cup actually means.

First of all, winning is obviously a team result. The talent and luck necessary for a goalie to win a Cup on the Detroit Red Wings is a lot different than what is required on the New York Islanders. The historical record shows that only strong regular season teams win Cups, so we need to look at the kind of numbers goalies put up on those teams. That said, hot goaltending does have an impact. At some point even a good team is going to run against other strong opponents in their quest for the Cup, and in those games superior goaltending can become a tiebreaking factor (e.g. the 2011 Cup Finals).

Here are the save percentages for each Cup-winning goalie in the save percentage era, adjusted to league average and normalized to the current average save level (.911):

1984: Grant Fuhr, .933
1985: Grant Fuhr, .925
1986: Patrick Roy, .946
1987: Grant Fuhr, .932
1988: Grant Fuhr, 913
1989: Mike Vernon, .930
1990: Bill Ranford, .934
1991: Tom Barrasso, .937
1992: Tom Barrasso, .926
1993: Patrick Roy, .945
1994: Mike Richter, .933
1995: Martin Brodeur, .934
1996: Patrick Roy, .931
1997: Mike Vernon, .932
1998: Chris Osgood, .923
1999: Ed Belfour, .933
2000: Martin Brodeur, .933
2001: Patrick Roy, .940
2002: Dominik Hasek, .923
2003: Martin Brodeur, .936
2004: Nikolai Khabibulin, .933
2006: Cam Ward, .928
2007: J.S. Giguere, .927
2008: Chris Osgood, .932
2009: Marc-Andre Fleury, .911
2010: Antti Niemi, .910
2011: Tim Thomas, .939

Those numbers are quite consistent. Twenty out of 27 goalies had an adjusted save percentage between .923 and .937. The average was .930 on 582 shots against. The only goalies to win the Cup with average save numbers were Fuhr in 1988, Fleury in 2009 and Niemi in 2010. Patrick Roy was the only Cup winning goalie to record a number of .940 or better, which remarkably he managed to do in each of his three Conn Smythe winning performances.

The overall averages for Cup Finalists were very similar, with an average of .927 on 572 SA. The distribution was different however. Eight of 27 had an adjusted save percentage of .939 or better, which reflects the fact that there have been a number of weaker teams that needed strong goaltending just to make it to the Final. Eight other Finalists had adjusted save percentages of .917 or worse. Some of those simply benefitted from strong teammates, while others were mostly good for three rounds and then saw their numbers nosedive as results starting going against them during the Finals.

This analysis gives the rough historical rule of thumb that to win a Stanley Cup, you need a goalie capable of putting up a .930 save percentage over 600 shots. That level of statistical performance doesn't guarantee a Cup, a number of goalies have played at an even higher level than that only to see their teams fall short at the final hurdle, but it makes a ring very possible if other variables (scoring, defence, injuries, opposition, etc.) also happen to break right.

Because of variance, nearly any goalie who makes it to the NHL could put up a .930 on 600 shots with enough luck, although it is not very likely to happen for a replacement level goaltender. According to the binomial probability function, a .900 talent goaltender would have a 0.7% chance of putting up that target number on any given 600 shot stretch. That means that even if they saw 600 shots against in every playoff season, they would still need to play in 99 of them to have a greater than 50% chance of going over .930 in one of them. Unless they happen to be astronomically lucky or find themselves playing for a complete powerhouse, I think it is fair to say that in general a .900 talent goalie is not good enough to win a Stanley Cup.

For a .905 goalie, the odds increase to 1.9%, still not even once every 20 times which is the usual cutoff point to determine statistical significance. The point where the probability moves above 5% is when the goalie's talent is .911, which is right about league average. The chances are much greater for one of the league's elite goalies. A .920 talent goalie would play at .930 or better over 600 shots about 20% of the time.

That shows that a top goalie on a contending team would have a reasonably good chance to win a Cup, but that it is still far from a sure thing. Goalies have short careers and often only a short window of opportunity to compete in the playoffs with a true contender. That is why it is not surprising that some elite goalies who conclusively proved their talent over hundreds of regular season games still never managed a deep playoff run. It was not because they weren't good enough to win a Cup, it was because they didn't get the breaks that are required to win a championship.

The idea that most starting goalies in the league are capable of .930 over 600 shots is also backed up by the actual statistical record. There are only seven teams who do not currently employ a goaltender that has put together at least one stretch of consecutive games with a save percentage of .930 or better on at least 600 shots against since 2009-10. Even among those seven, five of them have goalies who very narrowly missed the cutoff:

Reimer, Toronto: .929 on 622 SA
Theodore, Florida: .929 on 608 SA
Lehtonen, Dallas: .929 on 581 SA
Varlamov, Colorado: .931 on 563 SA
Brodeur, New Jersey: .929 on 603 SA

Some might quibble with the relatively unproven Reimer or Varlamov, or even the aging Brodeur, but I'll count all five as being close enough. That leaves just Columbus and Tampa Bay. Steve Mason's best stretch since '09-10 was .923 on 571 shots, while Roloson's best in the last two and a bit regular seasons was .926 on the same 571 SA. However, these numbers are from the regular season only; if playoff numbers count then from March 29 to May 19 Roloson had a .931 on 623 shots against.

Despite his hot spring last year, I think Roloson's age makes it unlikely that he will regain that form, and Mason's recent track record is simply not very good at all. I think it is probably fair to say that the Blue Jackets and Lightning may not currently have goaltending that is good enough to win a Cup. Other than that, every other team has a goaltender that has shown they can play at a high enough level for a long enough period of time that while they may not be a good bet to provide that level of goaltending during a playoff run, they would at least have an outside chance at winning a Cup if they were fortunate enough to be a member of a contending team.

This discussion should make it quite clear that evaluating a goalie's ability to win a Cup based on their past history is a woefully inadequate method. Nearly every starting goalie in the league is good enough to win a Cup in the right situation, and for a typical playoff team any netminder that is average or better should probably be considered good enough to win if they can just get on a hot streak at the right time. However, in any individual playoff season the odds would still be very much against them, even for an elite goalie on a contending team.

The only caveat to this analysis is that it seems likely that the threshold for a Cup winning goalie has dropped even further since the lockout. As Copper 'n Blue pointed out recently, there haven't exactly been huge gains in parity even with the salary cap system. As a result, goaltending performance has become less decisive than in previous seasons. Four out of six post-lockout goalies have been below .930, with two of them well below that mark. The numbers have dropped for Cup Finalists as well, who have averaged .923 since 2006. I'd estimate that the threshold is probably closer to .925 than .930 in today's NHL, which would leave only Columbus as a team without a goalie with the proven ability to perform above that level.

Tuesday, December 20, 2011

The Value of a Quick Start

I was one of a number of hockey observers who thought that by this point in time Jonathan Bernier would have mounted a serious challenge for the Los Angeles' Kings starting job, if not taken it over outright from Jonathan Quick. However, there hasn't been much of a goalie controversy at all, and there is no doubt that the 3rd round pick from Connecticut is the currently the clear #1 ahead of the highly-touted first-rounder from Quebec.

Is Quick a better goalie than Bernier? At the moment that seems obvious, based on their play over the last season and a bit and the way the team has distributed the playing time between them. However, it should be noted that Quick has a significant advantage in the battle between the two young goalies, having been born two years earlier. At the moment, Quick is 25 and Bernier is 23. For the sake of comparison, Jaroslav Halak was 25 and Carey Price was two months away from turning 23 when Montreal made the controversial move to trade their 2010 playoff hero away at the end of the postseason and bet on their younger goaltender. Quick is considerably more experienced, with an extra 180 regular season and playoff games in the NHL under his belt. That raises the reasonable question of whether Quick is the better goalie, or whether he is merely the more developed talent for the moment.

In addition to being a higher draft pick, Bernier had also had a better minor league career. If you compare the two of them by age, Bernier's progression was well ahead of Quick's through his early twenties.

At 19, Quick was still in high school, although he put up very good numbers. Bernier was recognized as one of the best goaltenders in the CHL, made the Kings out of camp and ended up with a brief cup of coffee in the NHL (4 games), before joining Manchester at the end of his junior season and starting 3 out of the team's 4 games in the AHL playoffs. Bernier also made Canada's under-20 national team for the world junior championships, while Quick was not selected to Team USA.

For his age 20 season, Quick went to UMass, where he would spend two seasons. At 20, Bernier was already a solid pro, posting a .914 save percentage in 54 games played as an AHL starter. The next year Bernier was even better with a spectacular .937 save percentage in 74 regular season and playoff games, earning the AHL's top goaltender award.

At the age of 22, Bernier joined the NHL seemingly for good as the Kings' backup goalie. He did fairly well as a backup (.913 in 25 games), although he didn't exactly take the league by storm as he had in the AHL. Compare that to Quick, who turned pro for his age 22 season which he split between the ECHL (38 GP, .905) and AHL (19 GP, .922), plus a trio of brief appearances in the NHL.

To summarize:

19: Quick in high school, Bernier AHL playoff starter
20: Quick in NCAA, Bernier AHL starting goalie
21: Quick in NCAA, Bernier AHL goaltender of the year
22: Quick ECHL starter/AHL backup, Bernier NHL backup

Up to that point in their careers, Bernier's development was clearly surpassing Quick's. However, things turned around in their age 23 seasons. Quick started the year in the AHL, but was called up to Los Angeles in December. When he arrived he made the most of his chance, playing very well early on in stopping 94.6% of the shots against and recording two shutouts in his first six starts. With Erik Ersberg and Jason LaBarbera both playing poorly, Quick ended up quickly taking over the Kings' starting job. Over the remaining 37 games he would play in that season, Quick's save percentage was .909, almost exactly league average (.908).

In his 23 year old season, Bernier also managed to record pretty average numbers in the NHL (.913 in 25 games), but he started very slow, losing 5 of his first 7 starts with a mere .889 save percentage. Bernier's early season struggles were magnified by the fact that Quick did very well out of the gate in the same 2010-11 season (7-1-0, 1.84, .936 in October of 2010), further solidifying his claim to the starting job.

This season Quick yet again began red-hot, going 6-1-2, 1.52, .947 in October, before quite naturally tailing off a bit since November 1. That was the third time in the last four NHL seasons that Quick was almost unbeatable in the first month he played, leading to some fairly extreme splits for his young career: so far:

Quick since 2008-09:
First month played: 23-8-4, 2.02, .928
Rest of season: 89-74-12, 2.72, .911

Compare that to Bernier, who for the second year in a row is off to a slow start.

First 7 games in 2010-11: 2-5-0, 3.30, .889
Remainder of 2010-11: 9-3-3, 2.13, .923
First 7 games in 2011-12: 2-4-0, 3.10, .883

Games at the start of the season often take on extra significance because they help establish a team's pattern of distributing starts between their goaltenders and the impact on a goalie's seasonal statistics is more noticeable. Look at how many fans around the league were either pronouncing their team's #1 as a Vezina candidate in November because of a strong early run of form or were panicking because their team's goalie took a while to discover their usual game. A hot or cold start takes longer to average out, whereas a slump in February or March has much less of an effect on a goalie's seasonal numbers to date because they may already have 40-50 games played by that point in the season.

The first few games can also be quite critical in terms of establishing a reputation for a young goalie trying to crack the NHL. It took all of five Jon Quick starts in 2008 before Los Angeles traded Jason LaBarbera to Vancouver and pretty much anointed Quick the starter. If those early starts had included a couple of blowout losses, then the team may very well have decided that LaBarbera wasn't actually that bad after all while Quick was in need of more seasoning in the minors. There is no doubt that Quick's hot streaks were almost perfectly timed to advance his career. The only way he could have timed them any better was if he managed to get on a real roll in the postseason.

I think there is a fair chance that Quick and Bernier are not that far apart in true talent, even disregarding the age gap between them. In the AHL, Quick put up a .923 on 1033 shots, while Bernier recorded a .928 on 3937 shots. Minor league success does not always translate to the big leagues, but it is at least evidence that the two were in a similar ballpark, even though Bernier was doing it at a younger age.

In the NHL, Quick's career regular season save percentage is .914 compared to Bernier's .906. However, if we exclude Bernier's four games at age 19, where he quite naturally struggled like the majority of teenagers do in the NHL at that age, and we add playoff numbers to increase the sample size, suddenly the career NHL save percentages for the two goalies converge quite a bit:

Quick: .913 on 6026 SA
Bernier: .911 on 925 SA

Quick's sample size is much larger, which means we are far more confident in our estimate of his true talent level. In addition, given that the majority of goalies are below average, it is safest to assume that a young goalie who hasn't proven much in the NHL is below average until he has faced a few thousand shots against. Bernier's pre-NHL track record makes it somewhat more likely that he is a real talent, but it is best to remain conservative at this point. Nevertheless, I will be very interested to revisit these numbers after the end of this season to see if they remain similar.

One thing that could be argued in Quick's favour is that his numbers have been trending upward over the last three seasons. However, I'm not sure how much to credit him for that given that his improvement has come almost entirely on the penalty kill.

2008-09: .926 EV, .869 PK
2009-10: .919 EV, .853 PK
2010-11: .921 EV, .903 PK
2011-12: .928 EV, .922 PK

Quick is a better goaltender today than he was in 2008-09, but he has also probably been very lucky on his last 435 shots against while shorthanded as .910 is an unsustainable PK SV%. For comparison's sake, Bernier's career numbers are .916 at EV and .890 on the PK (again, excluding his 19-year old season). Bernier may also have gotten a bit of luck on special teams, or perhaps the Kings' penalty kill has been unusually strong as of late, although his PK sample size is very small.

Looking at the progression and career numbers of the two young Kings goaltenders, it is hard not to wonder about the size of the impact of hot starts as well as Quick's opportunity to compete for the starting job in 2008-09 while there was not already an established starter, when Quick's two year head start in terms of age really turned into an advantage. Bernier is currently on pace to end his age 23 season with a career total of 49 games played. Jonathan Quick got into 116 of them in his age 23 and 24 seasons while competing mostly against Erik Ersberg, who was probably never more than a replacement level goaltender. Even if he starts playing better than Quick right now, Bernier will probably never get anywhere near that much playing time over this season and next.

If the crease didn't open up for Quick and he didn't have hot starts to begin nearly every season, it is certain that he would have played in fewer games, potentially many fewer games. The Kings brought Bernier along slowly, and it is possible that his development may have stalled somewhat given his infrequent usage as a backup goalie this season and last, whereas Quick went from an AHLer to an NHL starter in one season, and as a result his extra games played in the show at age 23 and 24 were likely very significant in helping him close the early career development gap against his teammate. That said, it is also possible that Bernier was never going to fulfill his earlier promise anyway. Even highly rated draft picks sometimes don't pan out.

This comparison reminds me of an article I wrote a while back which discusses the impact of opportunity on another Kings goalie, Jamie Storr. Storr was sort of the anti-Quick in that he was never able to put together a good run when it seemed like the starting job was available to be won, even though his overall save numbers were actually pretty good.

It's always hard to separate talent and luck early in a young goalie's career, when we really don't know enough about them to properly assess their true ability at the NHL level. Right now Quick is solidly ahead of Bernier, but has that been because of talent or opportunity? It may never be possible to figure that out with any degree of confidence, but the years ahead will give some additional information that will help make a more accurate estimate. For now, I certainly wouldn't rule out the possibility that Bernier is either as good Quick right now or that he will still eventually turn out to be better when both are in their primes. Los Angeles may be facing a Halak/Price type of decision at the end of next season when both goaltenders become free agents, and it will be interesting to what choice they will end up making.

Wednesday, December 14, 2011

What Does a Clutch Goaltender Look Like?

One of the most common goaltending cliches is, "It's not how many saves you make, it's when you make them." Colour commentators tell us this over and over again in their rush to credit goalies for wins or blame them for losses, and many hockey fans agree with them. Not every save is the same, they say. Saves that keep a team in the game or allow them to hold on to the lead are more important, and what happens when the game is already decided really doesn't matter so much.

Following that logic, a clutch goalie will make a higher percentage of saves when the score is close, giving their team a "chance to win". As such, we would expect them to have much better numbers in close games than in garbage time.

After the 2011 postseason, I don't think the people saying this kind of stuff really believe what they are saying. Either that or they simply don't recognize it when they see it. The reason for that claim is simply this: Strictly based on the above definition of clutch play (a goalie who performs better when the score is close than when it isn't), I doubt there are many goalies who have ever had more "clutch" numbers over the course of a single playoffs than Roberto Luongo in 2011. Yet, needless to say, Luongo didn't exactly get a whole lot of praise as someone who "made the key saves at the key times."

First, let's look at Luongo's stats at the series level:

Series tied: 7 wins, 1 loss, 0.97 GAA, .968 save %
VAN up 1: 6 wins, 4 losses, 2.56 GAA, .909 save %
VAN up 2+: 2 wins, 5 losses, 4.59 GAA, .868 save %

The Canucks never trailed in any series throughout the playoffs, and a big reason for that was their ridiculous goal prevention record when a series was tied. Luongo was particularly sharp in opening games, posting 3 shutouts in 4 tries.

On the other hand, when the Canucks went well out ahead of their opponents in the series they repeatedly suffered meltdowns. That's not particularly admirable, but the same logic that rates some saves are more key than others could be applied to rate some games as more important than others. And, if you do that, then any reasonable definition of those "key games" would have to include games where the series was tied, since a team that always wins when the series is tied could never be eliminated.

For the sake of comparison, here are Tim Thomas' numbers:

Series tied: 7-4, 1.39, .955
BOS up 1: 1-3, 3.11, .909
BOS up 2+: 2-0, 1.00, .967
BOS down 1: 4-2, 2.84, .921
BOS down 2+: 2-0, 1.50, .961

With the series tied or their teams up one game, Luongo's numbers were better than Thomas'. The main difference was that Thomas was great at closing out the Flyers series and he was also great in the two games where the Bruins faced 0-2 deficits.

Let's move on to the game level. Here are Luongo's numbers broken down by game score:

Lead by 5: 0 saves, 1 shot, .000 save %
Lead by 4: 0 saves, 1 shot, .000 save %
Lead by 3: 18 saves, 19 shots, .947 save %
Lead by 2: 56 saves, 60 shots, .933 save %
Lead by 1: 154 saves, 164 shots, .939 save %
Tie game: 257 saves, 276 shots, .931 save %
Down by 1: 84 saves, 92 shots, .913 save %
Down by 2: 24 saves, 32 shots, .750 save %
Down by 3: 41 saves, 45 shots, .911 save %
Down by 4: 14 saves, 17 shots, .824 save %
Down by 5: 2 saves, 3 shots, .667 save %
Down by 6: 0 saves, 1 shot, .000 save %

What's obvious from that chart? If the game was close, Luongo made a high percentage of the saves. But if it was a blowout, then everything went in. Down by 2 or more goals, Luongo had an .827 save percentage on 98 shots, which is almost unbelievably bad. In garbage time, Luongo made very few saves at all - with either team leading by 4 or more goals, he stopped just 16 out of 23 shots for a mere .696 save percentage. If I was a member of Vancouver's coaching staff, I'd be somewhat concerned by that number and what it could indicate about Luongo's compete level. That said, if it is only "when you make the saves" that counts, then his performance in blowout games should be considered meaningless anyway.

Copper 'N Blue also tracked scoring chances for all of Vancouver's playoff games. Because it is possible for goals to be allowed on non-scoring chances (which Luongo did four times in the Nashville series and six times in the playoffs overall), I calculated scoring chance save percentage as (scoring chances against minus goals against) divided by scoring chances against.

Lead by 5: 2 chances, 1 goal, .500 save %
Lead by 4: 1 chance, 1 goal, .000 save %
Lead by 3: 5 chances, 1 goal, .800 save %
Lead by 2: 29 chances, 4 goals, .862 save %
Lead by 1: 76 chances, 10 goals, .868 save %
Tie game: 127 chances, 19 goals, .850 save %
Down by 1: 50 chances, 8 goals, .840 save %
Down by 2: 19 chances, 8 goals, .579 save %
Down by 3: 26 chances, 4 goals, .846 save %
Down by 4: 5 chances, 3 goals, .400 save %
Down by 5: 2 chances, 1 goal, .500 save %
Down by 6: 1 chance, 1 goal, .000 save %

The numbers are pretty similar, although Luongo's numbers with the lead come down slightly relative to his trailing numbers, likely because of score effects. With the Canucks leading, the opposition took 2.2 shots for every scoring chance recorded. When Vancouver trailed, the ratio dropped to 1.8. Still, the overall conclusion is the same: Luongo's problems were not with the game close or Vancouver in the lead, but rather with the Canucks trailing by more than one goal. And in blowout games he apparently wasn't even trying (7 goals against on 11 scoring chances with either team leading by 4 or more).

Not surprisingly, Vancouver did a lot better in close games than in blowouts. Excluding empty net goals, they were 12-4 in games decided by one goal, 2-0 in games decided by two goals, and 1-6 in games decided by three goals or more.

Having said all that, let's compare Luongo's save percentages by score to those of his Stanley Cup goaltending counterpart, Tim Thomas:

Score within 1 goal: Luongo .931, Thomas .940
Up by 2 or 3 goals: Luongo .937, Thomas .944
Down 2 or 3 goals: Luongo .844, Thomas .957

Luongo was knocked for his ability to hang on to leads, especially during the Nashville series after giving up a couple of late tying goals, but his numbers while leading actually weren't too far off what Thomas was putting up for Boston. With the score close, Thomas again had an edge but not nearly as much as one would think based on their overall numbers. By far the biggest difference in performance between the two goalies was that Luongo was blown out repeatedly and did far worse when his team fell behind by two goals or more.

Did Luongo's awful play in blowouts have much of an effect on Vancouver's win/loss record? Maybe, maybe not. It would certainly be possible to argue that the Canucks would have been unlikely to come back in those situations anyway, especially with how anemic their offence was at times during the playoffs. On the other hand, Boston came back twice from two goal deficits, once again Montreal and once against Tampa Bay. If Thomas hadn't made the saves in those situations, the Bruins would quite possibly have never have made it to the Finals.

To me, the implications of these numbers are pretty clear. On one hand, you can choose to cling to the "key saves at key times", "the only thing that matters is clutch play" logic and praise Roberto Luongo for elevating his game in key situations with the score close in last year's Stanley Cup playoffs. Alternately, you could consider that most of the game is a "key situation", realize that effort and desire don't correlate perfectly with success, and understand that most goalies have the mindset to keep the puck out of the net at all times. That would cause you to reject the "key saves" logic, and instead rate goalies based on their overall performance. In that case, you would be perfectly entitled to knock Luongo's playoff performance, particularly relative to that of Tim Thomas.

That's assuming people are being logically consistent, however. In reality, there isn't an awful lot of logic involved in either hockey fandom or hockey reportage. When most people say "clutch goaltending", they usually simply mean "good goaltending". If not that, then they mean "goaltending behind excellent teammates". Another tactic is to move the goalposts, narrowing the sample size to focus on a few particular games (e.g. game sevens or Stanley Cup Finals games) as the only ones that qualify for the "clutch" distinction. I disagree with that logic since a team that didn't win in the earlier rounds would not have made it to the Finals at all, and similarly without winning three out of the first six no team would still be alive to participate in a game seven.

I've been in the camp that focuses on overall performance all along, so I'm not defending Luongo here. I think that throughout the 2011 playoffs, factoring in both his good and his bad games, Luongo was pretty ordinary. I do think that his play was better in close games, and I'm quite confident that if there was a hockey metric similar to baseball's win probability added, Luongo would rate much better according to that than he would based on overall save percentage. Whether that is a significant observation depends on your perspective on clutch goalies.

At this point I think it's also impossible not to accept the theory that Luongo has a higher-than-normal propensity to melt down when things turn against him. I used to agree with Tyler Dellow that it was essentially media narratives driving the perception, but the repeated blowouts involving Luongo and the above save percentage splits by score make that position tough to hold. I would still argue that Luongo's overall career playoff performance is reasonable relative to his true talent level, but has he ever had some forgettable single game performances on the way.

Thursday, December 8, 2011

Dave Bolland and the Percentages

It's fun early in the season to click around on Behind the Net and look at the huge variation in on-ice shooting percentage and on-ice save percentage for hockey players around the league. For example, Detroit's Drew Miller has a .988 save percentage behind him this season. Matt D'Agostini is at .980, benefitting from Brian Elliott's completely unexpected early season star turn in St. Louis. In San Jose, Martin Havlat and Michal Handzus are at .966 and .964. At the other end of the scale, Ottawa's goalies have been absolutely ventilated (.795) with rookie Stephane DaCosta on the ice, explaining his team-worst -9 rating. Steve Downie, Marty Reasoner, Craig Adams and Matthew Lombardi are other regulars with on-ice save percentages still below .850.

There can be huge differences even between teammates playing in front of the same defencemen and goaltenders. Da Costa's teammate Jesse Winchester has a .940 save percentage behind him, meaning a shot has been 3.4 times more likely to go in the net with DaCosta on the ice than with Winchester. There's obviously no way a forward could have anything even close to that much of an impact on shot quality. It's a similar story in Detroit, where nobody scores with Drew Miller, Cory Emmerton (.955), Darren Helm (.955), or Tomas Holmstrom (.960) on the ice, but perennial Selke nominees Henrik Zetterberg (.891) and Pavel Datsyuk (.904) get lit up. Some small part of that is likely related to quality of competition, but with those kind of ranges and samples it is mostly luck.

The same type of thing can happen over a postseason as well, given that a typical Stanley Cup winner plays 22-26 games, and when it does it becomes more widely noticed and emphasized because the whole hockey world is paying attention. An example of a player who has been absolutely rocking the percentages in the playoffs lately is Chicago's Dave Bolland.

A huge part of both the 'Hawks Cup run in 2010 and their almost-comeback against the Canucks in their first round series in 2011 was the ability of the team's checking line to outscore strong opposition. Bolland attracted a lot of attention for his work, and a good portion of those accolades are indeed deserved. Bolland is a key member of the Blackhawks because of his ability to play tough minutes and has a big impact on Chicago's team depth when he is in the lineup. However, over the last three playoff series he and his linemates were outscoring at a completely unsustainable rate.

Copper 'n Blue counted scoring chances for the Blackhawks' series against San Jose and Philadelphia in 2010, as well as the first round matchup against Vancouver last season. With Bolland on the ice in the 14 games he played over that stretch, Chicago created 49 scoring chances and gave up 69 against at even strength. Given the difficulty of his minutes in terms of opposition and defensive zone starts, that's really not too bad for Bolland and his linemates. The curious part is that at the same time Bolland's plus/minus somehow managed to end up at +13.

Excluding shorthanded and empty net goals, Chicago outscored their opponents 16-5 with Bolland on the ice at even strength. That means the team scored in over 1 of 3 recorded chances (34.8%), while the scoring chance save percentage behind him has been an improbable .922. Depending on who is counting them, typical rates are 1 goal scored per 6 or 7 scoring chances. If you add up those two numbers, you get a way-off-the-charts scoring chance PDO number of 1270.

I often write about how much luck there is in the playoffs, and how randomness plays a big factor in what kind of labels get applied to players. When you have a player who is both playing well and getting lucky it becomes very tough for the opposition to overcome, and perhaps equally tough for sportswriters to avoid hyping up the impact of that particular player. Focusing strictly on results in terms of goals for and against, it is hard to deny that Bolland had a huge impact on the last three series for the Blackhawks. However, the underlying numbers show that it would be virtually impossible for that level of outscoring to continue, as the percentages needed to be extremely skewed in Bolland's favour for the numbers to come out the way they did. I wouldn't bet on his line outscoring Joe Thornton or the Sedins again in their next postseason matchup.

This season, Bolland's percentages have been trending in the exact opposite direction, which explains why he currently sits at -5. Despite facing the highest QualComp on the team and starting in his own zone 33.9% of the time, Bolland manages to almost break even in terms of Corsi and the Hawks have actually outshot their opponents 124-112 with him on the ice at 5 on 5. All that indicates that Bolland is playing extremely well, but unfortunately his PDO so far is just 943, mainly because the save percentage behind him is just .868, and as a result he has been outscored 17-10. In the long run it typically all evens out.

Sunday, December 4, 2011

Pekka Rinne Comparables

Pekka Rinne's 7-year, $49 million extension from the Nashville Predators has been one of the biggest goaltending stories of this season. Before coming to terms on that huge deal, which was announced on his 29th birthday, Rinne had a total of just 188 NHL games played in his young career through the age of 28. There's no denying that Rinne had a great season last year and has been playing well for the most part in 2011-12, but that is still not a huge sample size to make a seven year bet on a goalie's future, particularly with the increased downside risk associated with a big money guaranteed contract in a capped league.

To help project how Rinne might be expected to perform through the entirety of that contract, I looked for other goalies since 1990 with a similar amount of NHL experience at the same age (150-200 games played through their age 28 or age 29 season), and selected only goalies who were starters for the last two or three of those seasons (i.e. goalies who had already peaked and had already become backups or washed out of the league were not included). To adjust for different scoring contexts, I also ran the goals over average numbers (calculated by subtracting league save percentage from each goalie's save percentage and multiplying by the number of shots). This was the career progression of those goalies by age:

25: 346 GP, .906, 30.2 GOA
26: 484 GP, .903, -18.3 GOA
27: 615 GP, .911, 74.3 GOA
28: 579 GP, .909, 40.2 GOA
29: 610 GP, .909, 53.2 GOA
30: 555 GP, .908, 28.6 GOA
31: 474 GP, .905, -20.6 GOA
32: 379 GP, .912, 39.0 GOA
33: 375 GP, .908, -9.3 GOA
34: 298 GP, .905, -35.6 GOA
35: 88 GP, .897, -21.8 GOA
36: 74 GP, .904, 0.1 GOA

Part of the reason for the steep decline in games played is that some of these goalies are still active and have not yet reached their age 36 season. However, the save percentage numbers show how the performance declined in the aggregate, especially from the age of 33 and onwards.

Of the goalies in the sample, four of them were particularly comparable to Rinne in that they had well above average save percentage performance in the three seasons prior to the cutoff. Those four goalies were Marty Turco, Miikka Kiprusoff, Guy Hebert, and Mike Dunham. Here are the same numbers for that quartet:

25: 100 GP, .916, 25.6 GOA
26: 104 GP, .901,-8.4 GOA
27: 108 GP, .918, 76.6 GOA
28: 84 GP, .913, 32.7 GOA
29: 87 GP, .915, 67.1 GOA
30: 120 GP, .913, 63.4 GOA
31: 124 GP, .904, -25.4 GOA
32: 96 GP, .912, 19.2 GOA
33: 132 GP, .908, 3.0 GOA
34: 136 GP, .904, -28.8 GOA
35: 35 GP, .897, -12.5 GOA

Through the age of 30, the four were elite at stopping the puck, worth an average of 2-3 wins each per season compared to an average goaltender. Once they got on the wrong side of 30, however, things went south pretty quickly. From age 31 to 35, they had a combined save percentage of .906, which was a whopping 44.5 goals below league average. Miikka Kiprusoff is still hanging around in Calgary, making $5.8 million per season and seemingly skating by without taking any blame for his declining performance, but the teams employing the other three goalies are no doubt very grateful that they didn't sign any of those goalies to long-term contracts.

That is why the Predators are taking on quite a bit of risk in signing Rinne to a seven year deal. Rinne may be an elite goalie today, but that doesn't guarantee that he will be one at age 32 or 35. Turco and Kiprusoff were once elite as well, both having led the league in save percentage and having been voted a postseason All-Star, and yet that didn't stop them from ending up ranked last and third-last respectively on the list of post-lockout save percentages for goalies with at least 200 games played.

Very few goalies are great throughout their careers. Those that are consistently elite typically break in early, usually taking on significant NHL playing time by the age of 22 or 23. Then again, that is not a hard and fast rule, as sometimes there are late bloomers like Tim Thomas who like Rinne came from relative nowhere to put together a pretty good initial three year run as an NHL starter after the lockout at the age of 31-33 (.914 save percentage). Then, instead of seeing his play decline like many others, Thomas only got better from there, winning the Vezina in two of the next three seasons.

Being from Europe and having less exposure to North American scouts may have contributed to Rinne waiting until his mid-twenties before winning a starting job. Rinne is not the first European netminder in a similar situation; Jonas Hiller had exactly the same number of games played through his age 28 season as Rinne. Hiller has been a quality netminder so far, but it remains to be seen how well he can sustain that level. He has also struggled in the early going this year after an extended absence due to vertigo, which has to be somewhat of a concern. Then again, even in a worst case scenario, Hiller has three years left on his contract at $4.5 million, meaning that Anaheim would have much less of a problem than Nashville if their starting goalie is unable to play up to his usual level.

Looking back six years to 2005-06, only 11 out of 30 starting goaltenders still hold down a #1 role today (and that's counting Brodeur, Khabibulin and Roloson as starters, all of whom may or may not still be in that position at season's end depending on how well they are able to stem the tide of old age). Just six of those 11 are still with the same team (Brodeur, Kiprusoff, Lundqvist, Fleury, Miller, Thomas). Competition for NHL starting jobs is fierce, and the odds are generally against a goalie holding his position for an extended period of time.

In the salary cap era, flexibility is important, and tying up a lot of money in a non-performing asset can be crippling to a team's chances of success. The evidence suggests that paying a goaltender $49 million for 7 years, particularly when that goalie wasn't an NHL starter until the age of 26, is generally not a good bet. Driving Play had it right when they concluded that Rinne would essentially have to surpass all historical comparables to outperform his contract. It is possible that Rinne stays healthy, happy and productive in Nashville, but there are simply so many things that can go wrong that the Predators will probably end up regretting their decision.