Unmasking AIHL Goaltending Statistics

As a goaltender for over thirty years, having played Junior A, college, Australian State, the Australian National Team and the AIHL, I was often frustrated when reviewing my stats because Wins, or Goals Against Average in my eyes were considered to be a team statistic.  Although Save Percentage is also provided, it too can be skewed depending on the quality of the team a goaltender plays for.

Goals Saved Above Average (GSAA) – An Alternative to Consider
In my research, I have identified there are a lot of new and exciting statistics being explored and published. Goals Saved Above Average (GSAA) is relatively easy to understand and, although it too has limitations, it establishes an average for the league and compares each goalie to the average-  creating a level playing field for comparing goaltender performance.

This is how it works. You take the league’s average save percentage and apply it to the amount of shots a particular goalie has faced. You get a number of goals that the average goalie in that league would have surrendered if they faced the same number of shots as the goaltender in question. That number gets compared to the number of goals surrendered by that goaltender, and a plus/minus is created. If a goalie is in the positive, that is how many goals they have saved compared to a league-average goalie. If they are in the negative, it is safe to assume that they are performing worse than how a league-average goaltender would perform in the same situation.

Formula
GSAA = [Shots against x (1 – league-average save percentage)] – goals allowed

GSAA Applied to the 2017 AIHL Season
Here is how the current AIHL goaltenders faired in the 2017 Season ranked by GSAA:

I am not affiliated with any team in the AIHL and I have not watched all the games other than the odd game in Sydney or a Fox Sports Game of the Week. However simply looking at the stats, I draw your attention to the following:

* Peter Di Salvo of the Perth Thunder has a Goals Against Average (GAA) of 2.54, Save Percentage (SV%) of 0.924 with a GSAA of 28.81 having played 28 games. Damien Ketlo of the Sydney Ice Dogs has a GAA of 2.77, Save Percentage (SV%) 0.923 but a GSAA of 30.04!

* If a goalie is in the positive, that is how many goals they have saved compared to a league-average goalie. In comparing the two goaltenders, we see the games played are the same, Peter has a lower goals against average and a higher save percentage in comparison to Damien. However, Damien’s GSAA is 30.04 compared to Peter’s 28.81.

Sydney Ice Dogs goaltender Damien Ketlo led the AIHL with a 30.04 GSAA in 2017

Strengths
* It is a very good statistic at equalizing goalies across the league, regardless of the team that they play for. For example, a goalie that has a .925 save percentage and has faced a lot more shots than average is actually playing better than a goalie that has a .930 save percentage and has faced fewer shots. The first goalie has faced more scoring opportunities and has saved more goals from going in based on their quality of play.

* It tells you how much a team relies on their goaltending to win games. If a team gives up a lot of shots but their goalie is continually bailing them out, their goalie will have a very high GSAA number. Those teams are more likely to struggle if their goalie goes into a slump or gets injured. Teams that succeed despite having a goaltender that is in the middle of the pack (or worse) in GSAA are actually more stable. If their goalie slumps or gets injured, they still have a very good chance to win using a replacement goaltender.

* It gives you a physical number of goals saved, rather than a percentage. It’s a statistic that can be very shocking. For example, the goalies illustrated previously have saved almost 28-30 goals from being scored on their teams in 28 games compared to a league average. A number that large will draw a lot of attention. It is a great statistic to prove both goaltenders’ worthiness to their teams. 28-30 goals saved is a very significant number.

Peter Di Salvo saved 28.81 more goals in 2017 compared to the average AIHL goaltender

Shortcomings
* Goalies that play more games will accumulate more goals saved.

* It does not take penalty killing into account. This is a major problem for some goalies that play for a team that is constantly killing penalties. Undisciplined teams will have goalies with a lower save percentage and a lower GSAA as a result.

* It does not take fatigue into account. Saves that are made after the 30-shot mark should be worth more, because goalies that face more shots than the league average will be more tired and will make fewer saves due to the poor quality of the team in front of them giving up more scoring attempts.

* It also does not take shot quality into account. This can be related to the number of penalties a certain team commits, or even a team’s quality of defence- but that would be difficult for any statistic to quantify.

GSAA is definitely not a perfect statistic. It has flaws, but it is more accurate than Save Percentage and should become more widely used in my opinion.

From September 1st, GSAA has been added to goalie stats under League Leaders on theaihl.com (Stats>League Leaders>Goalie Stats).