Attempting to Quantify Goalie Performance, or What happens when I get bored at work

Michael Steele

Living in Minnesota, it’s one of those state in the middle north of America, I have had few opportunities to watch my beloved Bolton Wanderers play a match in the last 12 months. Mostly, I have been resigned to listening to the acceptable to terrible radio call available through Player. As such I find myself turning towards statistical analysis (often not rigorous) to attempt to better understand how well (or not) Bolton is playing.

Today’s post was inspired by my curiosity over whether Bogdan or Lonergan played better last year (also, admittedly this post is fueled by a large heaping of boredom as I wait for revisions from my project lead). Now, there aren’t a lot of statistics out there that boil down a goalie’s performance, and/or the performance of the defense while the goalie is playing. In the chart below I’m attempting to quantify the each goalie’s performance by comparing how the team’s defense faired in terms of goals allowed versus the average goals scored by the opponent over the course of the season. This is by no means the perfect way to analyze goalie performance, but it’s a place to start.

Traditional Keeper Stats


New-fangled Made-up Keeper Analytics


One thing that jumps out right away is just how much worse Bogdan’s save percentage was than Lonergan’s last year. Another thing that jumps out at me is how Bogdan’s goals allowed number are affected by the crazy amount of PKs that Bolton gave up this past season. With the PKs included in his goals allowed Bogdan and the defense performed slightly worse than would be expected against the opponents that they faced. However, remove the PKs (there were 9 of them or 16% of the total goals allowed in Bogdan’s starts) and the defense is suddenly a little bit above average. Now, since the season isn’t portioned out into OC and post OC sections for the stats, it is possible that Bolton’s dreadful start to the season is unfairly reflected in Bogdan’s stats. In his 9 games, Lonergan put up a significantly better save percentage and outperformed Bodgan in the difference between in actual goals allowed and the expected goals allowed in both categories. However, 9 games is a relatively small sample size and could reflect a hot streak by Lonergan, the benefit of playing most of his games in the DF era, or it could be a reflection of his true talent.

Now, admittedly, there are a number of questions that this large snap shot of the season raises. Could Lonergan continue his statistical performance under a heavier workload? Will Bogdan’s statistical profile look different after full Dougie season? Is there a better way to attempt to quantify goal keeper performance? (Ok so the answer to this last question is yes, but then the question is what is it?)

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