An introduction to clearance maps

When I was busily logging all of those defensive stats to try and do something with individual defensive statistics (which will come first, a breakthrough in that or the next Game of Thrones book, eh, eh, amirite?) I started to come to the conclusion that, while clearances weren’t a great measure of defensive ability, they were a decent measure of the pressure a team has been put under.

After I stopped doing CB stats and started getting stats cravings again, I turned to clearances. From observation, I think they can be useful.

Sweden England U21s

Largely, I think you can divide clearances into 2/3 groups. The first is basically just the penalty area, or Red Zone. The second is a kind of trapezium shaped second box, or Orange Zone. This is a trapezium instead of a straight rectangle because at each side of it is a fairly non-essential area that full-backs occupy. These clearances generally, in my mind, aren’t too important, and don’t happen too often anyway.

This clearance map is for the Sweden U21-England U21 match. Reading it, it looks to have been an even match, both have similar numbers of clearances in total, in the Red Zone, and in the Orange Zone. Perhaps England put Sweden under slightly more pressure, as there seem to be a higher concentration of clearances in Sweden’s Red Zone, and England’s clearances give the impression of a higher line than Sweden, which suggests that the balance of play was pushed into Sweden’s half.

I didn’t watch the match, nor look at possession or shot stats before writing the above. England did indeed outshoot Sweden 14-10, getting more shots in dangerous areas too. They also had 58% of possession, which slightly surprises me, given how similar the clearance map looks. Perhaps England largely had control of the match, but failed to make it count in really forcing the matter, pushing Sweden back and creating chances, choosing instead to keep the ball and pass it around perhaps somewhat aimlessly (I can say this, I’m English).

So basically, that’s how you read a clearance map. Despite trying to push them, I’m still a bit hesitant about them. For one thing, I’m not sure how much I am reading into them what I want to read into them. I may not have known much about the U21 game, but I did know from the score that it was probably a close game with England edging it, which is what I read. Red Zone clearances will also be affected by corners, which could, in some cases, skew how the clearance map looks. Clearance maps will also work less well with Continental teams than English club sides, as they clear the ball far less. For example, season long clearance maps for the 2014/15 season champions from the La Liga and the EPL:

Barca 14-15 just BarcaMan City 14-15 just City

Below the heatmaps are rough Red Zone, Orange Zone, and ‘5th line’ totals. The 5th line total, in the EPL, is a rough proxy for how high the defensive line is. Man City is actually a bad example of this, because it very unusually goes down in total from column 4 to 5, then back up again at 6, which might suggest a brand of ‘charge and hope’ CB defending. For reference, in the Premier League, RZ totals are on average 550, OZ totals vary a fair bit, but usually between 200-300, and 5th line total EPL average is around 110. City are obviously a fair way below all of these.

However, Barcelona are HUGELY below these EPL totals, particularly the Orange Zone and 5th line, which are virtually non-existent. So perhaps, for now, keep a bit of distance from La Liga clearance maps.

Thanks for reading. Below is some more clearance map stuff that is less public-aimed, more stats-y.

I haven’t done too much correlational stuff yet, as I need to collect averages of everything and put it all together, but I have done it for one season, the Premier League 14/15. Total clearances per game had a -0.59 correlation with point totals, and ‘Red Zone’ clearances per game a -0.67 correlation. This is probably similar to why the Red Zone totals for Barcelona were much more comparable with the Premier League clearance maps than Orange Zone and 5th line totals. It also makes some sense. No matter how much you might want to pass the ball out of the back, there will always come a point (in your own box) where you’ve just got to boot it out of play and away from danger.

What next? Do more data-y stuff, to see whether Red Zone clearances are a good link to points totals elsewhere. Look more at clearance maps for other leagues outside of the EPL, to see if/how they can be of worth. Try and decide what clearance maps are actually *for*.

Can they explain why things happen, why teams win or lose, and thus how they can improve? It seems unlikely. They look like they can be used to tell the story of a match, or a general look at a team’s season, but is there any call for that?

Anyway, as usual you can comment below or get me on Twitter @ETNAR_uk


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s