Sunday, 28 October 2012

Passing networks

My dad sent me a link to an eBook called Objective Barcelona : How To Beat The Most Powerful Team In The World. It was free a few days ago, sorry for not advertising it sooner! It was quite an interesting read, it's a very extended essay, rather than a book. It was very editorial, in that it didn't have much data to back up it's arguments.

For me the most interesting topic in the book, was the discussion of Sergio Busquets. It suggested that cutting off the lines of passing to Busquets from the defense, forces Xavi to drop deep to pick up possession. Sometimes they swap positions, which is good because Xavi is more dangerous higher up the field. This got me thinking about passing networks.

I've seen some diagrams of passing networks from the MCFC data before:

I'm a bit fan of simplicity, so I think a first order attempt should be just plotting the passes. I'm sure plenty have people have done this already, but it's still informative.
Zero order figure. Blue lines show assists (passes leading directly to a goal). All passes successful and failed passes are included here.

My next idea was to start rounding the xy-coordinates to boxes, effectively binning the start and end points. It's not until we start rounding to the nearest 5% (10% in the y direction for scale) that we start to see structure. For the case where the boxes are 10x20% we've probably gone a bit too far for this particular data set.

Rounding to the nearest 5x10% box.
Rounding to the nearest 10x20% box

I think it's fair to say that Bolton play more directly, even in the non-rounded plot you can see the long passes towards the attacking line. It definitely looks like most of the lines go along the left to right axis, rather than up-down axis; especially compared to Man City.

This is another diagram which will be more interesting with more data. Hopefully with more data the main lines of passing will stand out. I also think there might be ways to make this more interesting: breaking the pitch into defined boxes, more detail in midfield; player-by-player analysis; some sort of directional analysis to show if the pass is arriving or departing at a particular point.

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