How Do You Stop Barcelona?

The short answer is: you can't. They almost always score, and they rarely ever let you score against them. That's a simple formula for winning.

The long answer is: you can affect how many they score. And if they score fewer, then you've got a better chance.

I started looking into this after Manchester City's match today against Reading. City had 17 shots (10 on target) but scored only one goal. Calls rang out that City "aren't good enough", but they rang hollow in my ears because I've seen the same thing happen to Barcelona many times, and Barcelona are the very definition of a good team. Indeed, it seems like many shots and few goals often go together.

The statistics bear out what I had suspected. Looking at Barcelona's last 10 games, we find that the number of shots taken is negatively correlated with the number of goals. That is, the more shots taken (in general), the fewer goals scored. Shots on target are also negatively correlated.

On its face, this seems odd. The more shots you get, the more goals you should score, right? This can fail to be the case, though, if both the number of shots and number of goals are both correlated with some other variable, but in different directions (one positively and one negatively).

What could that third variable be? The simple hypothesis is this variable is the tactics of the defense. In other words, if the defense takes one action, then shots go down but goals go up, while if they take a different action, then shots go up but goals go down. And as a result, it appears that taking more shots produces fewer goals.

Although there are many different defensive strategies, we can do a simple analysis by focusing on just two of them:

• Mourinho approach (a.k.a. "parking the bus"): a narrow, compact defense at the front of the penalty box.
  
  
• Wenger approach: a wide, compact defense moved high up the pitch.
  

Both approaches put 10 or 11 men behind the ball at all times and attack only on the counter.

The key difference between the two is in the positioning of the back line. With Mourinho's approach, you "invite pressure", facing wave after wave of attacks. However, with so many men right in front of the box, it is very hard for even Barcelona to find a way through. With this approach, they are certain to get many shots though.

With Wenger's approach, you keep Barcelona far enough away from your goal that they cannot shoot. Now, Barcelona must attack differently, by trying to break your offside trap. This is even harder to do, but when the offside trap is broken, it gives Barcelona a 1-on-1 chance against the goalkeeper. In other words, they will get fewer shots, but these shots will be more dangerous.

To determine which of these approaches allows fewer goals, though, we must look at the data. To do this, I used a simple measure: the average position of the center backs, be it 0, 10, or 20 yards in front of the penalty box.

Even though this is a fairly noisy measure and not a lot of data, we can see that it looks sensible, qualitatively. Centerback position is negatively correlated with shots on goal. In other words, the higher the back line, the fewer the shots allowed.

The important statistic, though, is how this relates to goals. And here we find a positive correlation. In other words, the higher the back line the more goals scored by Barcelona. This shows that Mourinho's approach is generally more effective.

It also means that Manchester City fans need not fret about scoring only 1 goal with 17 shots. It doesn't necessarily mean that the team is "not clinical enough". It may simply mean that the opponent used a tactic that invites shots but makes goals harder.

_{Note: This does not say whether Mourinho's or Wenger's approach is the better tactic for winning because we did not analyze how the position of the back line affects your own chance of scoring. What this does say is that Mourinho's approach makes Barcelona less likely to score against you.}