Thursday, March 22, 2012

Ilya Bryzgalov and Regression

Ilya Bryzgalov, first 27 games of 2011-12: .890
Ilya Bryzgalov, next 27 games of 2011-12: .929

Ilya Bryzgalov, last 27 games of 2008-09: .898
Ilya Bryzgalov, first 27 games of 2009-10: .925

It may still be too soon to proclaim that Ilya Bryzgalov is back in the kind of form that earned him a $51 million contract in Philadelphia, but the results have certainly turned around as of late for the Flyers' quirky netminder (8-1-1, 1.27, .955 so far in March).

As I pointed out in my post on Jon Quick, things that happen at the start of the season always seem to take on much greater significance. And when you have a slump in your first year in a new city that is notoriously tough on its goaltenders after signing a big-money contract in the off season and then end up increasing your exposure through a starring turn in HBO's 24/7 series, then any kind of early season struggles make it dead easy for sportswriters to start crafting narratives. There are all kinds of places to assign blame, from Bryzgalov's weak playoffs last year to his attitude and work ethic after signing his massive contract to his mental toughness and the pressure of the Philly market. It's possible to come up with all kinds of theories about the situation because while the performances were not up to par nobody knew for sure why exactly that was the case.

Is it possible that one of those things was affecting Bryzgalov? Probably, maybe even several of them at the same time. Insiders like Elliotte Friedman are most likely on the right track with some of the possible explanations for Bryzgalov's early-season play. Bryzgalov did look awful at times in games, worse than he did even when going through tough stretches in Phoenix, and it seems to be fairly unanimous within the team that he was struggling to cope with his greatly increased level of public exposure. At the same time, however, it is important to keep in mind the likely role of chance and variance in the goalie's results. As shown above, he has posted similar splits over a similar number of games before, even without the specific factors affecting his current season in Philly.

When a talented goalie goes into a slump, it can seem like they will never get out again. It's not always entirely bad luck, often they have to work on a few issues with their game or they have some off-ice problems, but with enough training and time those things are usually overcome and the goalie ends up returning to his elite form.

That's why regression to the mean is always the way to bet. If it's simply a matter of luck, then that is going to even out over time as shooters will stop making their shots at an unusual rate. If the goalie has issues to fix, then in most cases he will put in the time and effort to deal with them. At the other end of the scale, if a goalie's style of play is unusually effective then the rest of the league will do their homework on them to try to take advantage of any weaknesses and drag them back towards the norm.

Some have criticized stats guys' seemingly relentless focus on regression as removing the human variable and treating players like robots, but I think it is actually a natural consequence of human behaviour. When competition is involved, everyone copies everyone else and unsustainable advantages get erased fairly quickly. Those who excel may not always keep up the effort needed to separate them from the pack, while those who lag behind will often increase their intensity to try to make up ground. This is probably also one of the reasons why it is difficult to find persistent team advantages in terms of shot quality in today's NHL. A new system might initially work wonders but not once everyone else figures it out. In the long run, that often means there is not a lot of separation between the pack, especially when looking at a job like NHL starting goalie which only employs the top 30 best in the world at their craft.

Extended slumps by top level goaltenders are not a rare phenomenon. Sometimes they appear to have an obvious cause and other times they do not. Pretty much every goalie will struggle through them over the course of their pro careers. A particularly good example is when Henrik Lundqvist, whose consistently elite track record stacks up among the best in the game, had a 33 game stretch at .888 in the middle of the 2007-08 season that ended with him finishing third in Vezina voting. Dominik Hasek also found himself below .900 twenty games into the 1997-98 season that concluded with a second straight Hart Trophy. The Dominator recorded an identical .945 save percentage in the twenty regular season games both immediately prior to and immediately following those brief early-season struggles.

My philosophy is to deal with large sample sizes and bet on track record rather than recent form. Others prefer a "what-have-you-done-for-me-lately" approach that tries to take into account all kinds of other factors such as a goalie's mental state, his recent technical performance or the way the rest of the team has been performing. Both methods will get some right and some wrong, but I think the historical evidence suggests that betting on established talent over recent form is a far more successful method (just read Arctic Ice Hockey, Gabe Desjardins has been beating that drum for years). Ellen Etchingham also recently provided a great read on the subject of variance.

Even if there was someone out there who could identify all of Bryzgalov's early-season technical flaws and could see between his ears well enough to perfectly measure how the pressure of his new environment would impact his play, they still might not do any better at predicting his next 27 games than somebody who simply knows that Bryzgalov is a .915 career goalie on 10,000+ shots. All Bryzgalov may need to do is tweak a few things in his game, change his mental approach, or have his team restructure some aspect of his environment and it might be enough to reset everything and put him back to his usual self, leaving that detailed analysis of his struggles pretty much obsolete.

I don't mean to oversimplify the difficulty of fixing holes that have developed in your game, that is not always an easy process or something that happens overnight. And if you are the Philadelphia goalie coach, then obviously nothing is more important than diagnosing exactly what is going awry. But for proven talent, things usually end up working out in the long run, or at least until they hit the inevitable decline because of age or injuries.

Bryzgalov is unquestionably a proven NHL talent, but while he has quieted the critics for the moment the playoffs are certainly going to be a pressure cooker where every small performance sample will be blown ridiculously out of proportion. Hopefully for him when those games roll around he will be closer to his March form than his level of play in October, or the media will no doubt be dusting off the exact same stories about his inability to handle the pressure of Philadelphia.

Friday, March 16, 2012

The Curse of Obama

In the 20 games since the Boston Bruins' White House visit that Tim Thomas famously did not attend, the defending Vezina Trophy winner has gone 9-9-0 with a very uncharacteristic 3.07 GAA and .890 save percentage.

That .890 would look ugly for pretty much any goalie in today's NHL, but it looks especially glaring for Thomas considering his excellence over the past three seasons. Going back to the start of 2008-09, Thomas' numbers have been consistently elite even when divided up into the relatively small sample size of 20 games (playoffs included):

Nov '11-Jan '12: .935
May '11-Nov '11: .943
Mar '11-May '11: .929
Jan '11-Mar '11: .931
Nov '11-Jan '11: .939
Mar '10-Nov '11: .941
Dec '09-Mar '10: .911
May '09-Dec '09: .921
Feb '09-May '09: .936
Dec '08-Feb '09: .930
Oct '08-Dec '08: .937

The .911 and .921 came in the latter half of 2009-10 when Thomas was limited by a hip injury. If that is enough to excuse those two results, it has been over three calendar years since a healthy Thomas had to endure a 20 game stretch below .929. And then he decided to skip a team event for personal reasons and everything fell apart.

Obviously I don't actually think the flap surrounding Thomas and President Obama made any significant impact on his play, but there is no question that regression has hit the Bruins hard in net in 2012. Not only have Thomas' numbers nosedived, but Tuukka Rask is 0-3-1, 3.07, .886 since the All-Star break. The .940 team save percentage that the team was rocking early in the year was never going to hold up, but I didn't expect the wheels to come off this heavily either.

At 37, Thomas is in the age range where performance levels can change pretty suddenly, and he has had a lot of recent mileage considering his workload this year combined his playoff run last season. Thomas is already in the top-10 all-time this year for games played by a 37-year old, and including playoffs only one goalie has ever played more games in his age 36 season than Thomas' 82 last year. That doesn't necessarily mean that an awful 20 game stretch is a sign of impending doom, but it's certainly something to keep an eye on. Thomas' recent form has to be at least somewhat concerning for Bruins fans with the playoffs just around the corner, given that elite goaltending has been a big part of the team's success over the past two seasons.