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05-07-2012, 11:51 PM
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Hockey Outsider
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Goalies: Adjusted Playoff Save Percentage

I don’t think that anybody has done a comprehensive study about playoff save percentage. I thought it was an important enough topic to spend a couple of hours analyzing the data.

To adjust playoff save percentage, two adjustments are required. First, saves are normalized to a 90.5% save percentage environment. This is calculated for each goalie each year, and the goalie’s shots and saves are removed from the league for the purpose of that calculation. Second, these numbers are adjusted to an environment where goalies face 28.6 shots per game. This won’t impact save percentage in any year (as shots and saves are adjusted by the same amount), but it ensures that a goalie’s performance in a year that features many shots per game (such as 2011) is not weighed more than a goalie’s performance in a year that features few shots per game (such as 2001) when calculating career averages.

I haven't attempted to account for the fact that a goalie on a strong team will be able to play more games due to having better teammates, facing an easier first round opponent, having home ice advantage, etc. These are important things to consider, but I can't quantify them.

I’ve used data from 1984 to 2011. All numbers are taken from hockey-reference.com. I realize that playoff save percentage exists going back to the 1950s, but this is the only usable data that I have. If someone wants to continue this project going farther back, I’d welcome it.

I’ve stated before that save percentage is, in my opinion, the single best statistic to measure goalie performance. That being said, I think that save percentage is more reliable in the regular season than in the playoffs for a few reasons. First, the sample sizes are much larger, which means that one can have more confidence in the numbers. Second, the strength of opponents varies widely in the playoffs (a goalie can play 300 minutes of hockey entirely against the best team in the NHL). Third, many teams play more defensively in the playoffs – on average, I think that many teams surrender less dangerous shots, which would, all things being equal, overstate save percentage in the playoffs. Still, to the extent that save percentage is used, it should be adjusted for era.

My purpose isn’t to present one number which is a perfect representation of a goalie’s performance. Rather, I want to improve on what has already been quantified in conventional statistics.


Last edited by Hockey Outsider: 05-07-2012 at 11:58 PM.
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