Wednesday, May 14, 2014

2013-2014 NHL Regular Season Goalie Consistency

At the end of the regular season I ran the numbers for NHL goalies and found that Tuukka Rask, Semyon Varlamov and Carey Price were the top three NHL goalies for this season using Wins Above Average (WAA).  WAA is the marginal value of a goal against divided by two (since each win is worth two standings points) times the number of shots on goal that a goalie faces times the difference in the save percentage of the goalie and the average save percentage of all goalies for that season in absolute value (since a goal against has a negative effect on team wins).  Here is a step-by-step guide to calculate NHL goalie performance.

Now what I want to do is figure out how consistent NHL goalies are from one season to another, so I am comparing the regular season performance from last season (which was shortened due to the lockout) and this season.  To do that, I am going to only look at goalies that started at least 10% of the regular season games played for each season, since the number of games played is different between the two regular seasons.

Thus to find how consistent NHL goalies are in consecutive regular seasons,  I am looking at the percentage of NHL goalies who are in the same WAA quantile in consecutive regular seasons and those who have moved up or down one quantile from one season to the next.  Here is a step-by-step guide on measuring player consistency.

What I find is that of the NHL goalies who started at least 10% of the total number of regular season games, 30.8% were consistent (in the same quantile in each season), 32.7% were near consistent (either moved up or down one quantile from one regular season to another) and 36.5% were inconsistent (moved two or more quantiles from one regular season to another).

Of those that were consistent, there were only three NHL goalies who were in the top quantile (i.e. top 20% of NHL goalies in consecutive regular seasons).  They are Tuukka Rask (Boston Bruins), Sergei Bobrovsky (Columbus Blue Jackets) and Henrik Lundqvist (New York Rangers).  Given that Tuukka Rask was the most productive goalie (but just barely) and that he is also only one of three goalies to be in the top 20% from one season to the next, I would say that he is the best candidate (statistically) for the Vezina Trophy.