Blocked shots don't typically make the highlight reel. Of course, they don't, you might say - they're a non-event. Well, they are, and they aren't. They're an event that wasn't of much consequence in the scheme of things. But they are still "events" in the way that that the good folks at companies like Opta think about them.
To me, the answer is mostly no. Virtually all teams had between 65-70% of their shots blocked or miss the goal. If we had to pick a club that did particularly well, it would be Arsenal; only 65% (64.72 to be exact) of their total shots were off or blocked.
The upshot: most shots don't make it anywhere near the goal. And the best teams aren't much better than the worst ones in turning their possessions near their opponent's goal into great opportunities. Instead, the name of the game seems to be the number of such possessions and the ability to turn high quality opportunities into the stuff that really counts - goals.
In any case, I've been wondering about blocked (and other kinds of) shots lately. Lots of times, statistically minded fans and commentators will talk about shots as a measure of offensive or defensive team performance. Creating shots or not conceding them is generally taken to be a good thing. Hard to argue with, really, and that's not the point of today's post. Instead, I was wondering to what extent shots on or off - which is typically what we see in box scores - reflect the full panoply of shooting that happens in a match. Maybe, the little statistics nag in the back of my brain might say, there's a selection effect. Are we looking at a particularly interesting subset of shots, rather than all of them? If so, we may be under-estimating the real odds of shots creating chances in a match.
Thanks to the excellent Guardian Opta chalkboard feature and data I collected from last season, we can take a look at that to see the full profile of shots in the Premier League. So to start, below is the overall distribution (in percentages) of all shots taken in the league last season, categorized by goals (shots on target that went in), shots on target, shots off target, and importantly, shots that were blocked. I find this last category particularly interesting, because they are the shots that never really were.
As the graph shows, the most common category of shots are those that go off target; over 40% of all shot attempts fall into that category. It's not quite 1 in 2, but its not all that far off. The second most common category is blocked shots, it turns out, as about a quarter. So combined, shots off target and blocked shots comprise 70% of all shots. Who knew?! I certainly didn't. In contrast and predictably, goals make up slightly less than 10% of all shots, and about 1 in 5 shots are actually on target (21.3%).
So far so good. One question these numbers don't answer is whether some teams were particularly good at avoiding blocked or off-target shots. The next graph provides the answer.
To me, the answer is mostly no. Virtually all teams had between 65-70% of their shots blocked or miss the goal. If we had to pick a club that did particularly well, it would be Arsenal; only 65% (64.72 to be exact) of their total shots were off or blocked.
What's more remarkable to me is the overall consistency in the distributions across teams; about 65-70% of shots were off target or blocked, and about 30-35% found the target, give or take. So there's roughly a 1:2 ratio in terms of shots that survive to create a real chance to those that meet a premature or unfulfilling end. The big differences come into play when we look at the shots that actually were on target. Here, the better clubs simply have a much better conversion rate of turning accurate shots into goals. Of course, these are also the clubs that produce more shots overall.
The upshot: most shots don't make it anywhere near the goal. And the best teams aren't much better than the worst ones in turning their possessions near their opponent's goal into great opportunities. Instead, the name of the game seems to be the number of such possessions and the ability to turn high quality opportunities into the stuff that really counts - goals.
