After four advanced stats articles breaking down the prowess of skaters, it’s time to head to the crease and help you further examine goaltenders. The next stat up in our series of Advanced Stats for VGK Dummies is GSAA or Goals Saved Above Average.
For those who are baseball fans, this is essentially WAR (wins above replacement) for goalies. For those who aren’t baseball fans, smart thinking, baseball is boring.
Usually, we first try to explain what the stat is before we get into the formula of how it’s calculated, but this one is a bit convoluted when explained that way that we’ll start by simply saying, GSAA measures individual goalies against the league average goalie. That’s all you need to know, now follow through how it’s calculated.
First, we need to calculate the league average goalie. To do so, we take every save made by every goalie in the NHL and divide it by every single shot on goal over the course of a season.
To simply the numbers let’s use a hypothetical using just one game. Say the first game of the season there are 50 total shots on net, 25 by each team. A total of five goals are scored, so 45 shots are saved. Thus, the league average is 45/50=0.900.
Now, we take an individual goalies stats. Let’s say he gave up one goal on 25 shots, meaning he saved 24.
GSAA = [Shots against x (1 – league-average save percentage)] – goals allowed
So, our goalie faced 25 shots, he allowed 1 goal, and the league average is 0.900.[25 x (1-0.900)] – 1
[25 x 0.1] – 1
GSAA = 1.5