I asked the nice people at Infostrada Sports Group for a whole slew of data with regards to penalties taken in the Premiership and they were kind enough to provide me with it. They can be found online and on twitter.
When I asked for the data this was the only post I planned to do but it seemed a waste not to be a bit more thorough, hence the wait. First is just a little quirk I noticed when working through the data; you’re more likely to take a second penalty if your first one is missed/saved than if it is scored:
I don’t have a sensible explanation for that. The table also shows that the outcome of a players first penalty has no impact on future penalties (conversion rate is the same whether the first penalty was scored or missed).
There’s another interesting piece to pull from the second half of that table. The conversion rate of ‘subsequent penalties’ is 84%, which is well above league average. Therefore ‘first penalties’ must be scored at a level far below league average. So how large is the discrepancy?
In six posts about penalties I think this is the second time I’ve found something statistically significant. Players are much more likely to miss their first penalty than any subsequent ones they take. Nerves would be my best guess. It’s funny – whenever a penalty is saved the main reason I’ve heard commentators give is that the ‘keeper has studied where the striker had placed his previous penalties. I think this kind of makes a mockery of that assertion.
Anyway back on topic; last time I looked at teams and found that, with the possible exception of Chelsea, no team had a measurable level of skill when it came to taking or saving penalties (link). Not even the best teams. So does this translate to players? Here’s the funnel plot for penalty takers:
So to re-iterate, the bold line is equivalent to the league average penalty conversion rate and the two dotted line represent two standard errors above/below the mean. The dotted lines become closer as the sample size in creases because there is a larger sample over which the effect of random variance decreases. I’ve only added labels for players with >10 penalties. If there’s someone you want to know the specific stats on ask in the comments and I’ll get back to you.
In summary this plot is telling us that we can’t be sure there is any player is better at taking a penalty than any other. Hurray.
Say we briefly assume that the numbers here actually reflect each players true talent (they don’t) and we place hypothetical Frank Lampard (89.7% conversion) in a penalty shootout against hypothetical Alan Shearer (77.8% – basically league average). The shootout has the usual rules, five rounds followed by sudden death – how often would you expect hypothetical Lampard to win the shootout? I’ll let you take a guess and put the answer at the end of the post.
But enough with strikers. Do any keepers possess an ability to saving penalties?
Same story. In fact the grouping here is almost unnaturally tight. There’s no skill here, a ‘keeper could let in the first 13 penalties they face and we still wouldn’t be certain that they were below average.
I’ll do a summary of this series soon but in short: With a few exceptions (home vs away, first penalty vs subsequent penalties) a penalty is a penalty is a penalty. It doesn’t matter which team it is awarded to, who takes it or who the opposition ‘keeper is, at the end of the day our best guess is that it will be scored 77% of the time.
I think that’s it for penalties, as far as I can tell I’ve exhausted the numbers I’ve got, it’s probably time to move on anyway. That being said if anyone has any requests or ideas for anything else I could do with these numbers then let me know
*Even though he misses less than half as often as hypothetical Shearer, hypothetical Lampard would still only win 75% of the shootouts. In order to win the shootout 90% of shootouts hypothetical Lampard would have to score 96% of the penalties he takes.