In previous articles, I've explored the relationship between a players ability to hit the target and over/under-performing his expected goals (xG). In this article I will continue this exploration of the data from the xG Ineractive Tables from American Soccer Analysis, focusing on the 2015-2017 MLS seasons.
As seen in Exploring Shots in MLS, some players are indeed better or worse than the average (34%) at getting their shots on goal. So for this analysis, I will break the players into four different groups before comparing them. These are those players who had less than 20 shots in total, those whose 95% confidence interval of on-target percentage was below average, those who were around average, and those that hit the target more than the average. The summary statistics are in the table below.
|<20 shots||Below ave||Average||Above ave||Grand Total|
Some interesting things to note here. Most players have taken less than 20 shots over the course of those three seasons, and they are pretty bad at it as well. Further, about 10% of the players are either above or below average. Those that are below average at hitting the target seem to select poorly when to shoot, as their xG/shot is just 0.062. Even so, they further underperform their xG with an efficiency of just 0.7. Not too surprising since they manage to get less than 20% of their shots on target. Combined with those that take few shots, almost 100 goals are "lacking" based on what xG would predict.
Focusing on the average group, we can see that they are indeed average. Granted, they take about 2/3 of all the shots, so this makes sense. Compared with the two previous groups, they pick better shots and has an efficiency around 1. Again, this is to be expected since these players make up the vast majority of all shots taken.
Now what about the remaining 33 players. These are the ones that consistently hit the target more regularly than everyone else. Their xG per shot is also much better, which suggest that the majority of their chances are good ones. It also makes sense that their on-target percentage is higher, since they probably have more shots inside the 6-yard box than outside the penalty area. Even so, they get 45% of their shots on target, and outperform their xG with an efficiency of 1.15. And while they were expected to score 21% of the goals, they ended up scoring 24% of them.
So who are these players? In the interactive graph below, each point is one player who had at least 20 shots. Above average finishers are marked in purple while below average are in red. The size of each bubble corresponds to the amount of shots taken, and the green line is the weighted regression line of approximately 3. Just hover over each bubble to get info on the player that made it. For mobile version, click here.
A word of caution
As can be seen, there really seem to be a relationship between getting shots on target and the ability to outperform xG. However, there is of course some individual variation here. Further, while this can offer some explanation why a player is better or worse than expected, it is not necessarily predictive. For instance, seeing that Cristiano Ronaldo has only hit the target on 15 of 55 shots (27%) this season in La Liga help explain why he is underperforming there. Especially compared with 16 of 37 (43%) in Champions League, or 636 of 1517 (42%) the last five seasons. He will probably revert back to the mean (either his own or the total one), but based on this analysis alone that is harder to predict.
Even with that caution though, this analysis seem to be further evidence in support of the original conclusion. Just hit the target!