Basic goalkeeper statistics are too simple to be repeatable or useful. It is easy to look up a keeper’s save percentage or goals against average, but in the end those stats are so heavily reliant on quality of shots on goal faced that they are not a good indicator of keeping skill. Instead, let’s look at Premier League keepers in sample sizes that go beyond single seasons and focus on the role of shot locations, as well as those of the resultant saves and goals. The charts below default to all shots faced by keepers 2010-present in the English top tier. All hexagons are sized based on the volume of shots, saves, and goals. The visualization really comes alive once you click on either a) the name of a keeper to focus both charts on his shots faced and their outcomes and/or b) a zone in the top chart to see only save and goal locations below that came from shots that area.
What do we make of all this? First, while I’ll note some of my takeaways below, this dashboard is a representation of Opta data (mined by Paul Riley, @footballfactman on Twitter) containing over 150,000 shots of goal, and there are over 500 combinations of keeper and shot zone that can be selected here. I invite readers, especially those who have focused on a particular keeper’s club in the 2010s, to explore perspectives relevant to their interests and offer their own interpretations in the comments below, Twitter, reddit, or their own blogs. Please mention me on Twitter click to see my Twitter account for the last 3, as I really look forward to seeing others’ interpretations of this data. That said, here are my thoughts after sifting through these data while creating the dashboard:
1) A Keeper’s chart is an invitation for further investigation, not a final judgement.
While some keepers come across as more impressive (Adrian, with only one significantly below-average zone) than others (Wayne Hennessey, with 8 bad areas), it is probably more productive to view keepers in terms of opportunity for improvement and apparent relative strengths. For example, let’s compare some keepers in the middle range of the metric driving the bar chart on the left, Pepe Reina and Hugo Lloris:
Here we have keepers with “bad” zones that never overlap. What do you make of these zones in which the keeper’s save percentage falls below average? Their own coaches might focus film study on those areas to see if the keeper has exhibited bad positioning tendencies that cost goals when facing shots from there (Reina in particular seems to have one particular angle to his left that was consistently problematic). If so, they can orient training around correction of the issue. Opponents might gameplan to specifically target the keeper’s “weaker” positions (Lloris is so strong near goal that Spurs opponents might not want to stress so much about working hard to create prime opportunities and instead let fly as soon they get an opening inside the box), though this could well be easier said than done.
2) When not shooting from straight on, far post shots seem to produce more goals.
While overall we see goals being scored in a largely symmetrical fashion, if you focus on shots to the left or right, keepers seem to have a harder time protecting the far post than the near post.
Note here that the data driving this presentation are limited to on-target attempts, so further study may be needed to discover whether strikers miss the goal mouth more often on far post shots than near post ones.
3) Major differences from the norm are particularly important.
On this topic I can’t help but pick on Wayne Hennessey, and by extension Crystal Palace.
The highlighted hex differences in the top chart are common among all keepers, as no one aligns very well with shot volumes or save percentages from all locations, but the differences in goal locations is quite unique to Hennessey and his club. Why is he allowing so many goals towards the center of the goal mouth? This data doesn’t include keeper positioning, speed of buildup, etc., so it’s hard to say if this trend is more a reflection of Hennessey errors, or his defense forcing him into extremely disadvantageous situations. As I mentioned earlier, sometimes exploration of these data mostly lead to asking a smarter, more focused question than providing irrefutable answers.
Again, do any patterns stick out to you while exploring these keeper trends? Insights from those who have followed a few seasons of a particular keeper’s club(s) or who want to delve into spinoff video analysis would be particularly interesting, as I have been looking at this from a much broader perspective. I’d love to read your thoughts in the comments below, Twitter, reddit, or your own site.