FC Barcelona won again, their seventh in a row across all competitions, with a 3-0 triumph over Girona. It was a bit of a weird one, though, with Girona scoring two own goals. Girona also took more shots than Barça, 13 to 11, according to WhoScored.
And it's not like Girona were just peppering hopeful shots from outside the box, in fact it was Barcelona who were taking more speculative efforts. Just 31% of Girona's shots came from outside the box, with 62% in the 18-yard box, and 8% in the 6-yard box. Meanwhile, 44% of Barcelona's shots came from outside the box, and 56% within the 18-yard box, and none within the 6-yard box.
This isn’t something new, either. Eibar outshot Barcelona 13-11 despite losing 1-6. Getafe lost 1-2, but took 13 shots to Barça's 7. It's the same with Juventus (lost 0-3, outshot Barcelona 13-9). It wasn't the case against Espanyol, Alaves, or Betis, as Barcelona outshot both teams by a factor of more than 2.
Now, shot counts obviously aren’t everything. If they were, Barcelona wouldn’t have won all of those six games.
But this trend is backed up by, for example, expected goals graphics made by Michael Caley. To explain it quickly, where shots are taken from and the situation they were taken in (for example, where they were assisted from or whether the player made a dribble before shooting) are taken into account. Better shot types leads to a better chance of goals.
If a team has more goals than their expected goals, that means they are doing better than expected given the quality of chances. If they have less, it means they are doing worse than expected.
Not everyone that puts forth an xG number is calculating it the same way, so it can be difficult to compare them if you get them from different sources. For consistency, I’ll be using his only.
Expected goals stats are in their relative infancy, as is statistical analysis of football in general. This is by no means the gospel, but let’s take a look.
Top teams have a tendency to overperform xG anyway, but Barcelona have been doing it more than usual so far this season. On the other hand, Real Madrid have underperformed.
Here are a few examples.
xG map for Barcelona - Eibar.— Caley Graphics (@Caley_graphics) September 20, 2017
Last two Barca matches: 18 shots, 2.8 xG (incl penalty), 8 goals. That's some kind of efficiency. pic.twitter.com/tKlbzQ9IB9
Against Eibar, Barça “should have” gotten 1.7 goals + a penalty, let’s say that’s 3 goals. Instead, they got six. As Michael writes, they’ve done it a bunch.
Let’s look at Real Madrid-Levante
xG map for Real Madrid - Levante.— Caley Graphics (@Caley_graphics) September 9, 2017
Real Madrid “should have” gotten about 3 goals to Levante’s 1. Instead it was 1-1.
Let’s look at another one:
xG map for Getafe - Barcelona.— Caley Graphics (@Caley_graphics) September 16, 2017
I'm just going to take a drink of water as I check out how Barca walked their La Liga match today... pic.twitter.com/3z3wkSasrQ
Barça “should have” scored 0.4 goals, essentially, maybe not even 1. Instead they scored two and won 2-1.
Here’s Real Madrid-Valencia
xG map for Real Madrid - Valencia.— Caley Graphics (@Caley_graphics) August 28, 2017
So, Valencia should have had about 1 goal to Madrid’s 3, but instead it was a 2-2 draw.
I think you get the point. So what does this tell us? Well, there are two possibilities:
- Barcelona are overperforming compared to their “fundamentals”, whereas Real Madrid are underperforming. Essentially, Barcelona are getting slightly lucky and Madrid slightly unlucky. Both teams will regress towards where the xG says they should be, Barcelona will lose more and Madrid win more.
- Barcelona are just better at converting chances than Real Madrid. We then expect this trend to hold. Both teams may regress a little, but not a lot. Barcelona may not overperform their xG as much, but they’ll still overperform a lot.
- The model has it all wrong. Barcelona are creating chances just fine, Real Madrid are not. We are expecting the wrong number of goals.
So to go back to the original question, it’s hard to say which scenario we’re in. However, I’m inclined to think it’s either scenario 1 or 2. In other words, Barcelona are either on a hot streak that could go away, or they’re unusually efficient.
And most likely, we’re in a blend of the two scenarios. Barcelona probably are in a hot streak that will end, but I don’t think they’ll stop overperforming their xG. For example: they do have Lionel Messi, he’s going to be more efficient than the vast majority of players. He’s going to score more goals than you’d expect from certain positions.
This is something to follow as the season goes on.