Penalties. They are are almost always controversial, and perhaps even more so now that we have VAR and La Liga still finds a way to get the call wrong. Interestingly, though, as Villarreal fans we had a very good year on the penalty front, drawing 10 of them, the second most in the league. We were level with Real Madrid on penalties until Sergio Ramos dove under no contact whatsoever and gave them 11 for the year.
Diving, or attempting to draw penalties, if often seen as an effective but honorless way of producing offense. Get in the box, feel some contact, go down. But I my question is whether that is actually the most efficient way to behave in the box. I do not know that I have all the data to prove it, but I suspect that staying on your feet may actually be more efficient from an expected goals (xG) perspective than trying to draw a penalty.
Three Villarreal players drew multiple penalties this year, Chukwueze, Moi Gomez, and Gerard Moreno. Nabil Fekir led the league with five penalties drawn, which is downright remarkable. (Enes Unal actually drew three, if you’re interested.)
Best case scenario drawing penalties
Focusing on Fekir, the most successful player in Primera at drawing penalties, he was also fouled more than anyone else in the league: 113 times. That’s 43 more times more than Lionel Messi if you can believe it.
Fekir averaged 3.45 shots per 90 minutes on the field and 0.06 goals per shot. (He took one penalty). His non penalty xG per shot was also 0.06.
Outside of Fekir, Betis drew one other penalty this season. The six penalties added 0.15 xG per 90 to the team. or 0.95 xG per penalty drawn (fbref).
Now, here’s where things get speculative. Let’s say that Nabil Fekir is actively trying to draw penalties each game, so he gets into the box and he goes to dribble a defender, there’s a little bit of contact, but instead of going down he stays on his feet and launches a shot that’s 0.15 xG at the goal. That’s not an especially high average shot, but if he does that once in a game he’s added as much xG as the penalties do to the average over the course of the season.
Now instead, let’s say he feels contact and then goes down, but the ref doesn’t think it’s a penalty. They turn the ball over and that xG never happens. Let’s say this situation repeats itself three times in a match and he never gets his penalty call. That’s 0.45 xG he turned down for a chance of getting 0.95xG that never came.
Spread this out over the course of a season, let’s say he stays on his feet an extra two times per match in the box. He gets 5.02 touches in the attacking penalty area per 90 minutes he’s on the pitch (on average) and shoots 1.8 times per 90 in the penalty area. If he can get 1.5 extra shots off per 90 in the box at 0.15 xG per shot he’s more efficient from an xG perspective than if he goes down twice per 90 and only gets a penalty call once every 439.5 minutes like he did this season.
A more normal example
Now, our example was with the person most successful at drawing penalties. If we apply that to someone like Chukwueze, who successfully drew two penalties. That’s one penalty every 1008 minutes he’s on the pitch. Samu averaged 5.54 touches per 90 in the attacking penalty area and only took 1.1 shots. His two drawn penalties gave the team 0.02 xG per match averaged over the whole season, which means if Samu just shot once more per 90 in the box he would gain the team more xG even if the shots were only worth 0.03 xG on average, which inside the box they almost all are worth more than that.
The piece of data I don’t have that I need to flesh this out is how many times players are going down in the box overall. If I knew how often Chukwueze or Fekir were going down relative to their 5-5.5 touches in the box per 90, I could estimate better exactly how much xG they are giving up by not shooting, and I could also calculate what the chances are of getting that 0.95 xG penalty call when you go down in the box. My suspicion is that it’s very low.
There will be times when a player goes down in the box when they can’t help it. They either lose their balance or there’s legal contact or there’s a heavy foul not called and they just can’t stay on their feet. That’s part of the game. However, given how rare a drawn penalty is for every player in the league (even the player with the most) it seems to me that it is more efficient from an xG perspective to stay on your feet and attempt a shot than to dive and hope the ref gives you a call.
Diving isn’t just bad sportsmanship, it’s stupid football.