Great goaltending can have a huge impact on the NHL standings. Sergei Bobrovsky won the Vezina Trophy with a League-leading .931 save percentage last season and helped to boost the Columbus Blue Jackets by 32 points in the standings, from 76 points in 2015-16 to 108.
The impact of great goaltending may be clear, but figuring out which goalies are capable of such outstanding performances can be a bit murky. In particular, what can be expected of Bobrovsky in 2017-18, along with the two other finalists for the Vezina last season, Braden Holtby of the Washington Capitals and Carey Price of the Montreal Canadiens?
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The issue with projecting goalie performance is that save percentages are so volatile. After all, who could have predicted Bobrovsky's .931 save percentage in 2016-17, given his .908 save percentage in 2015-16? This was not an isolated case; Bobrovsky's save percentage also improved from .899 in 2011-12 to .932 in 2012-13.
Given this volatility, the safest course of action is to assume that a goalie's save percentage will approach a weighted average of the past few seasons. To project a single season, statistician Eric Tulsky, who is manager of analytics for the Carolina Hurricanes, suggested basing the projection on the previous four seasons, weighted at 10-7-5-1. That is, Bobrovsky's save percentage for 2017-18 can be estimated by adding up all of his saves and shots over the past four seasons, but multiplying those in 2016-17 by 10, those in 2015-16 by seven, those in 2014-15 by five and those in 2013-14 by one. That places greater emphasis on more recent data and results in a weighted save percentage of .923, slightly above his career average of .920.
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Repeating this process for Holtby also yields a .923 save percentage. Even when stretching it to the ten-thousandths column, Bobrovsky and Holtby remain tied, at .9231. Holtby has an edge on Bobrovsky when taking it to hundred-thousandths, .92312 to .92306. That works out to one goal every 15,653 shots, suggesting that expectations should be the same for each goalie in 2017-18.
Using Tulsky's method, Price has a .927 save percentage, which is far greater than his .920 NHL career average. A closer look at Price's data reveals that the difference may be goaltending coach Stephane Waite, who was hired July 4, 2013. Prior to Waite's arrival, Price had a .915 save percentage in 310 NHL games. Since Waite was hired, he has a .928 save percentage in 199 games, first among active goalies who have played more than 20 games in the League.
Although Price can be projected as the favorite for the Vezina Trophy in 2017-18, we need other stats to separate Holtby and Bobrovsky. One way to do that is to consider the quality of the shots each goalie has faced. If either goalie's numbers are being boosted from facing a larger share of shots from the outside and fewer while killing penalties, then those numbers could fall as soon as those favorable conditions come to an end. However, the difference between the two goalies is minor regardless how they are compared.
A goalie's save percentage is lower when killing penalties because he's facing the top opposing shooters while his team is at a numerical disadvantage. Using the same weighted four-season average, Holtby has a .931 save percentage at 5-on-5, .942 at 5-on-4 and .873 at 4-on-5. For Bobrovsky, it's .930, .938 and .884. So, it looks like Holtby has a slight edge at even strength and on the power play, and Bobrovsky has been slightly better shorthanded, but neither goalie has a clear advantage overall.
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The location of shots can also impact a goalie's save percentage. Holtby had an .873 save percentage on shots taken inside hockey's so-called home plate area -- from the goal posts to the faceoff dots, then up to the top of the faceoff circles and across -- and a .966 on shots from outside. Bobrovsky had an .878 save percentage on home-plate shots and a .965 on shots from the outside.
So, that signals that Bobrovsky has the edge from up close, that Holtby has a very slight edge on outside shots, and that Holtby's overall numbers may have been boosted by the Capitals keeping more shots to the outside.
Considering these and all other available goaltending metrics, there appears to be only one area where either goalie has a noticeable advantage: quality start percent. A quality start is awarded any game when a goalie's save percentage is above the League average of .913. From this perspective, Holtby has a four-year weighted average of 61.8 percent, which is 2.9 percentage points better than Bobrovsky's 58.9 percent, or one extra quality start for every 34.5 games. As minor as that seems, that could be the greatest difference between these two goalies.
It may be impossible to distinguish between Holtby and Bobrovsky from a statistical perspective, but it's reasonable to project a .923 save percentage for each of them. That will place each of them in the mix for the Vezina Trophy in 2017-18 -- but well behind Price, whose save percentage projection is .927.
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