Tuesday, January 17, 2012

Vezina Trends

"First, he leads the NHL in the one stat that trumps all others: wins." (Scott Burnside, ESPN)

Going after Scott Burnside on goalie analysis is not dissimilar to shooting fish in a barrel, but my real beef is with how he is parroting the conventional wisdom that people within hockey consider wins to be extremely important. It might be Burnside's opinion that wins are the most vital stat, which is obviously misguided but he is allowed to personally believe whatever he wants. The problem is that when he explicitly claims to be handicapping the Vezina race, then at a minimum I would expect that he should be aware of what stats have actually been considered to be important in past voting.

Here is how the last 20 Vezina winners have ranked in five key goalie stats (GVT is Goals Versus Threshold):


Some readily apparent observations from the above table:

1. It is very rare for the consensus best goalie to win the most games. Only 4 of the last 20 Vezina winners led the league in wins. In contrast, for each of the other four stats, the Vezina winner was more likely to lead the league than not. Wins are in fact easily trumped by save percentage, GAA, shutouts, and GVT.

2. The data suggests that the emphasis on shutouts may be decreasing as well, although that could just be variance.

3. The 1996, 2003 and 2004 decisions stand out quite starkly relative to the others. The unwillingness of voters to rank non-playoff goalies as the best in the league was a big factor in the '96 and '04 votes, which is at least somewhat understandable although I disagree with the logic. That leaves the '03 Vezina as the most unusual result of the last two decades. Voters overlooked a playoff goalie that had 1-1-10-5-1 ranking based on the above table, a pattern that much more closely matches the overall averages than that year's winner.

4. The historical pattern that goalies require an excellent GAA to win a Vezina has continued. I would suggest that a low GAA on a strong defensive team seems to be the biggest source of error in the current voting, as those goalies appear on ballots much more frequently than average goalies that rack up a lot of wins on strong offensive teams.

Tuesday, January 10, 2012

Grant Fuhr and Effort

One of the things people like to say about goalies on dynasty teams is that they didn't try as hard when it didn't matter, and as a result their stats were understated. I think the evidence generally suggests that while there are some score effects from changing team strategies, goalies usually do try to keep the puck out of the net at all times. With only 30 starting jobs available goalie competition is fierce, which makes less likely that goalies would be willing to slack off while in the game. Even good teams have to fight to make the playoffs these days (see the '10-11 Chicago Blackhawks as an example), which means that there can be major team consequences for a netminder with a habit of trying to coast though a game here or there. Finally, in today's low-scoring environment there is not a lot of garbage time so goals against in blowouts simply will not have a material impact on a goalie's stats.

However, while those things may be true at the moment, they don't necessarily apply to results from several decades ago where the competitive balance and scoring level was much different than it is in today's salary capped NHL. I do think it is probably worth checking truly dominant teams to see whether there are some kind of unusual effects at play, since the incentives for players on those teams are not exactly the same as they are for everyone else.

For example, I suspect that some members of the 1980s Edmonton Oilers may not have been playing much of a 200 foot game during the second half of the regulation schedule during the peak of their dynasty simply because they were already dozens of points in front of everyone else in the standings. With 16 of 21 teams making the playoffs in those days, there was really nothing to left to do by that point in the season other than pad their offensive stats while trying to stay healthy and in good shape for another attempted Cup run.

From 1983-84 to 1987-88 (numbers from the Hockey Summary Project and Hockey Reference), there is a noticeable downward trend in Grant Fuhr's save percentages by month as the season wore on:

Oct: 1121 SA, .898
Nov: 1288 SA, .889
Dec: 1181 SA, .870
Jan: 1286 SA, .890
Feb: 1128 SA, .871
Mar: 1158 SA, .880
Apr: 232 SA, .871

It could be argued that Fuhr was experiencing fatigue, but that seems unlikely as a factor (other than potentially in 1987-88 when he played in 75 games) because he was usually used in a platoon scenario together with Andy Moog. On top of that, Fuhr's numbers jumped back up again to October levels as soon as the playoffs started.

To summarize:

Oct-Jan: 4876 SA, .887
Feb-Apr: 2518 SA, .875
Playoffs: 2268 SA, .899

By the end of January, the Oilers were always sitting very comfortably in the standings.

1983-84: 38-9-5, 41 pts ahead of 5th
1984-85: 36-9-6, 45 pts ahead of 5th
1985-86: 36-11-5, 40 pts ahead of 5th
1986-87: 34-14-11, 36 pts ahead of 5th
1987-88: 29-17-7, 26 pts ahead of 5th

The only season the Oilers were not ranked first overall in the league was 1987-88, where they sat in third place but were still far above the playoff cut line. In all five seasons the team had more wins at the end of January than the last place team in their division would finish with at the end of the season, meaning they could have lost every game they played after January 31 and still made the playoffs. In short, the Oilers had very little to play for as a team from February onwards in any of those seasons.

Looking at Andy Moog's monthly numbers, there is some reason to believe that the rest of the team was having a big impact on the late-season statistical slide:

Andy Moog, 1983-84 to 1987-88:
Oct-Jan: 3363 SA, .890
Feb-Apr: 1572 SA, .876
Playoffs: 343 SA, .866

Moog showed a very similar save percentage decline, suggesting that the Oilers as a group were less committed defensively once they had the division well locked up. Either that or Moog and Fuhr both had a similar lack of focus late in the season when the games became less meaningful. However, given that the two were mostly alternating starts, and were at least in some level of competition for the starting job come playoff time, I would guess that team defence may have been a more significant factor than the effort level of each individual goaltender.

I think there is a reasonable argument to be made that Grant Fuhr's true talent in terms of save percentage was understated by his regular season numbers in the mid-1980s. From 1983-84 to 1987-88, his overall regular season save percentage was .884, a decent mark given the league average of .876 over the same period of time. However, if his February to April numbers are excluded as not being representative of a team giving 100% defensive effort in front of him, with his playoff numbers substituted instead, Fuhr's save percentage would jump to .891, nearly doubling his advantage relative to league average. That rate would also rank Fuhr up near the top of the league over that period of time, rather than merely the upper middle of the pack.

It is still worth pointing out that Moog would be at .888 based on the same assumptions. That suggests that Edmonton's shot quality against was probably not nearly as bad as some suggest, at least when the team felt the game mattered and wanted to play defence, although Moog was an above-average goalie in his own right.

Other goalies may have suffered slightly from this effect as well during the unbalanced '80s, but it seems likely that it would have had the biggest impact in Edmonton given their prolific offence and incredible team success. Fuhr may still be a bit overrated by some fans who rate him as one of the main keys to the Oilers' championships, but this is at least some evidence that supports the contention that he had Hall of Fame talent in his prime.

Wednesday, January 4, 2012

Anything Can Happen in One Game

As Canadian world junior fans learned yet again yesterday, anything can happen in a one game playoff. By now the more reactionary fans are well into their usual routine of blaming the goalie and/or the coaching staff, but all that really needs to be said is that the format of international tournaments works against the best teams and creates a high degree of randomness. The recent history of world junior and Olympic tournaments speaks to that, with some of the huge upsets that have taken place, together with the oft-repeated story of teams that looked like world-beaters through four or five preliminary games (as Canada did in this year's tournament), before unexpectedly falling to an inferior foe because of one bad outing in an elimination game (and as far as poor games go, it's certainly possible to do much, much worse than outshooting the opposition 56-24).

The international tournament format caused me to think of an interesting hypothetical: What if the NHL postseason was a series of one-and-done showdowns? Obviously it's not possible to replay those postseasons based on that counterfactual, but it is possible to just look up the results for the first game of each playoff series. It's not a given that things necessarily would have turned out the same way if both teams knew it was do-or-die, but it's probably a fairly reasonable approximation.

It turns out that having a single game elimination format would almost completely alter NHL history. Out of the last 22 Stanley Cup champions, only one of them never found themselves trailing 1-0 in a series at any point in their postseason run. The 2008 Detroit Red Wings are the only Cup winner to win all of their series openers in a single playoff season since Edmonton traded Wayne Gretzky. Every other Cup champion since then lost an opening game, meaning that if they were playing a one game series they would have been eliminated and would never have earned the chance to drink from Lord Stanley's mug.

It would have been a similar story, although not quite as extreme, if all series had been best-of-three affairs. In that scenario, the clear majority of winning teams would still probably not have made it all the way through to win as they did. Fifteen out of the 22 teams lost 2 out of the first 3 games in at least one series on their way to a Cup. Even if the format was changed to a best of 5, that would still have a major impact on the final results, as somewhat amazingly half of the eventual champions trailed 3-2 after five games at some point during their Cup run.

In total, based on these assumptions, Cup winning teams since 1988-89 would have won 61.4% of one game playoffs, 76.1% of three game playoffs, and 87.5% of five game playoffs.

That supports the obvious fact that the larger the sample size, the more likely it is for talent to win out over luck. At the world juniors, it's obvious that Canada routinely has the most talent. Over the past five tournaments, Canada has a record of 26-5 with a goal differential of 185-65. Some portion of that is from pounding on the minnow nations, but even against the traditional top five hockey nations (USA, Sweden, Finland, Russia, Czech Republic) Canada still went 15-5. That's a .750 winning percentage, and the goal differential suggests that the team's record was fully earned (the Canadian juniors scored 99 and allowed 56 against the same opponents for a Pythagorean expected winning percentage of an even slightly better .758).

That's an incredibly dominant record, but it still leaves the simple reality that if Canada is a 75% favourite in back-to-back playoff games against two solid opponents, that still leaves them with only about a 56% chance to win any given tournament. Given the talent of some of the American, Russian and Swedish squads in recent years, that's almost certainly overstating the odds of even a truly dominant team getting through two single elimination contests unscathed. The odds drop even further if the team did not secure a quarterfinal bye by finishing first in their pool.

This is not a simple attempt to justify a loss. Winning a single elimination tournament is also less meaningful, for the exact same reasons. Sometimes a weaker team wins, sometimes a good team plays poorly but gets the breaks anyway. The longer the series, the less variance and the more confidence that the better team ends up triumphant. All Canadian hockey fans would like to claim that the 2010 Olympics win proved that Canada is the world's best hockey nation, for example, but that tournament alone is not enough to prove that assertion. A better argument would be to look at Canada's overall record in winning three of the last six best-on-best tournaments, but even that analysis would show that it is relatively close between the top nations. At the end of the day, many Canadian fans need to have more reasonable expectations about how much success to demand from the teenagers representing their country internationally.

The international format is what it is, it's certainly exciting and it's not going away any time soon, but it's still important to not try to draw too much significance from such a short tournament. If you are tempted to do so, just remember that if the same rules applied to the NHL playoffs, a different team would probably end up winning well over 90% of the time.

Tuesday, January 3, 2012

40 Year Old Goalies

There was a discussion in the comments to a post over at Arctic Ice Hockey a couple of weeks ago about whether Tampa's goaltending (current team mark: .896) will regress back towards league average over the rest of the season. Over time goalie save percentages will nearly always move towards a goalie's career average. At the moment, Mathieu Garon is playing at close to his established level (.907 this season, .904 career) while Dwayne Roloson's seasonal rate is well below his career mark (.883 and .909 respectively). It looks like it is reasonable to expect major improvement from Roloson, which should boost Tampa's numbers the rest of the way.

However, while I am confident that Tampa's team save percentage will continue to move upwards towards league average, I do not believe this will be because Roloson's numbers will get a whole lot better. It will instead occur as the team shifts more playing time to Garon, who started 11 games to Roloson's two during the month of December, or perhaps through bringing in another goaltender if GM Steve Yzerman decides to address his team's crease situation. Roloson's numbers will probably improve, if nothing else playing in more of a backup role against weaker opponents may help slightly, but the reasonable expectation is that at 42 years old he is simply too old to expect him to produce anything north of .900.

Looking at the career records of goalies in the save percentage era past the age of 40, it is impressive how much the top two on the list stick out both in terms of quantity and quality of performance:

Hasek: 3366 shots, .914
Roloson: 3602 shots, .907
Everyone else: 4899 shots, .891

Hasek and Roloson each have two of the top four seasons among the 40+ crowd. Other than them, Ed Belfour is the only one who managed to keep his starting job past the age of 40, although his numbers were much lower. Everyone else had numbers that were below league average, in most cases well below.

1. Hasek, 2005-06: 43 GP, .925
2. Roloson, 2010-11: 54 GP, .914
3. Hasek, 2006-07: 56 GP, .913
4. Roloson, 2009-10: 50 PG, .907
5. Joseph, 2007-08: 9 GP, .906
6. Belfour, 2006-07: 58 GP, .902
7. Hasek, 2007-08: 41 GP, .902
8. Burke, 2006-07: 23 GP, .901
9. Belfour, 2005-06: 49 GP, .892
10. Roloson, 2011-12: 17 GP, .882
11. Joseph, 2008-09: 21 GP, .869
12. Esposito, 1983-84: 18 GP, .859

Based on those comparables, a good bet on Roloson's current save percentage talent is probably in the .895-.900 range, although with perhaps 15-20 starts remaining Roli's actual performance could still vary quite widely.

Assuming Garon keeps up his current level of performance and keeps getting the majority of the starts, Tampa's save percentage will probably improve by something like .010 the rest of the way. For example, if Garon keeps his .907 through the end of the season while Roloson plays at .895 and the shot split between them moves from the current 57/43 to 67/33, the Lightning should end up with a save percentage of .903 over their last 50 games. That's still well below league average, which is why the team should certainly consider making a move if they want to make a stronger playoff push this season. History suggests their current goaltending will be unable to perform at a league average level, which will make it difficult for the Lightning to catch up in the standings.