Everyone agrees – standard goalkeeper stats like Goals Against and Save % vs Shots On Goal don’t tell anything meaningful about keeper ability. A great keeper on a weak team will have a high GAA; a mediocre keeper behind a strong team will have a lower GAA. Assessing a keeper often comes down to watching them play – and then going with your gut.
Does Stopper provide a more objective way to analyze keeper performance? To test and validate Stopper data for developing players, we’ve been tracking stats on several pro keepers. Today we’re going to share our data on the Vancouver Whitecaps keeper, David Ousted: a consistently strong player with over 10,000 minutes logged in MLS and a 2015 finalist for MLS Goalkeeper of the Year.
If you’re not familiar with Stopper, here’s a snapshot of the data we pull from a typical game – in this case, Whitecaps vs the Sounders on Sept. 17, 2016. The final score was 1-0 – but from a GK’s perspective, here’s the data that matters. (I should note here that we don’t really track the “Communication” metric for recorded games since its too noisy to hear what the keeper is saying!) Despite conceding a goal, Ousted made some solid saves including a nice reflex tip on an Ivanschitz ball at the 60′ mark.
Now let’s look at aggregated Saves for the Whitecaps 2016 season (below). As one would expect the majority of saves (24.5%) occur in the central quadrant of the goal. But over the course of the season, a strong trend emerged – even though Ousted made a similar amount of saves on both sides, he caught and held more shots on his left and tipped away more shots on his right. From that we can infer that a) there may be a general tendency for right-footed strikers to aim wide on keeper right or b) Ousted is more comfortable catching and holding the ball on his left.
Here’s where it gets interesting! When reviewing the heat map of Goals Against, we can see an inverse correlation with saves. Of the 52 goals scored against Ousted in 2016, 32.7% were scored in the lower left quadrant of the net – almost double that of the lower right at 19.2%.
Obviously there are a lot of other factors that come into play in individual games (for example, a low far post goal might come from a header off a cross, or a shot from a surprising angle that catches the keeper off guard) but the aggregated season numbers seem to tell a clear story: the odds of scoring against Ousted on the lower left hand side are more than double when compared to the other quadrants of the net. And if comparing shots on goal vs goals allowed, overall scoring on the left hand side was almost twice as likely as on the right.
We’ll look at Distribution in a separate post as we wrap up our first analysis of a MLS keeper over a full season. Does Stopper provide a more objective way to analyze keeper performance? We’ll need to evaluate a few more pro keepers as we continue testing the app but early indicators are looking good: there may finally be a better benchmark for evaluating goalkeepers even at the professional level.
While the current version of Stopper is designed for developing keepers, we are working on a “professional” version that allows more detailed data capture and analysis, including video capture linked to Stopper data metrics. We’re looking for clubs or organizations that would like to do beta testing – drop me a line if you’re interested!