By Sean Steffen (@seansteffen)

The topic of “finishing” is always a fun one in the analytics world, and, last April, it’s one I studied using data going all the way back to the beginning of the league to see if I could find evidence for a statistically significant gradient of repeatable finishing skill in MLS. Click the link to read the piece in full, but the short of it was, while there were many instances where a forward outperformed their xG by a wide margin or converted an unusual number of their shots on goal, these seasons were rarely repeated within a player’s career as you would expect if such numbers were tied to a skill.

After such a long and arduous study, you can imagine my consternation any time I read a piece praising or criticizing a player’s finishing skill within the league. In fact, when Jordan Morris told the New York Times, “my finishing is still raw,” I nearly had an aneurysm. Doesn't anyone read long winded statistical articles anymore?

Of course, I accept that long held beliefs don’t change overnight, and, although I am generally a cynic, when I look at what has happened with baseball over the last few years and how analytic concepts have worked their way into the broadcast booth and the columns of newspapers and blogs, I also recognize that this is not a hopeless cause.

All we analysts can do is put our noses to the grindstone, publish works, and champion the works of others. With this in mind, I recently set about exploring an aspect of finishing which I have long wondered about: heading.

Let me explain. While Michael Caley was able to find evidence of finishing among a small handful of elite, high volume shooters in Europe, I found that such a tier of player does not seem to exist in MLS. One thing which we both found was a clear delineation between the goals above expected goals of defenders as compared to the goals above expected goals of forwards. In both the EPL and MLS, forwards are more broadly better at putting the ball in the back of the net than defenders.

In the broadest of sense, finishing skill does exist when comparing attackers and defenders, and the best hypothesis as to why has to do with the amount of finishing practice that forwards take in training. Now, for those who feel I may have contradicted myself, it should be clarified that most of my claims about finishing are not made at such a macro level.

Defenders and Forwards may display finishing skill differences, but once you start comparing forwards to each other you’ll find, outside of a very small handful of players in Europe, little to no evidence there is any gradation of the skill among forwards. Presumably the repetition of practice largely standardizes the skill.

But the vast majority of our data supporting this comes from shots taken with the feet. An interesting question to raise is, what about headers?

Going into this study, I hypothesized that the skill of accurately heading the ball could be less standardized than striking it with the foot, which could mean that players who specialize in heading the ball (Kei Kamara and Alan Gordon spring to mind) might be able to consistently outperform the expected goals model on their headers in a way that we do not see from forwards in this league when we look at all shots.

So, let’s dive into the numbers.



From 2011 to 2015, MLS saw 6,562 headed shots. From those shots, 2,145 were on target and 723 of them were goals. That gives us an average league conversion rate of 11.02% headed shots and 33.71% for headed shots on target.

Headed Goals vs xG in the aggregate

The first test is a simple one. We need only take the xG from all 6,562 of these shots, which, in this case comes out to 715.67 expected goals, and compare that to how many goals were actually scored—723. That’s only 7.33 goals over xG over 5 full seasons of soccer.

But how does that compare to shots taken with the foot from the run of play?