By Sean Steffen (@seansteffen)

Earlier this year, I decided the world needed a 30 page paper on shot limiting in MLS. Of course, the powers that be found this to be a tad self indulgent, and more accurately, sad that I had the time to do such a thing. They ended up talking me down to a slightly more readable 20 pages, which can be read here.

But my art will not be compromised, gosh darnit! There is still so much to be learned about this topic, and, more to the point, my obsession hadn’t been quenched. Several questions were raised within the paper that I simply didn’t have the necessary data to explore.

Chief among these had to do with the positioning of defensive lines. In part two of my paper, I plotted each player’s passes per game against defensive actions per game, in order to get a rough estimate for where on the field each players were getting their defensive actions. Though less than ideal, it was a novel work around in the absence of actual positional defensive data.

The initial data suggested that teams that limit shots tend to evenly distribute defensive actions along multiple defensive lines, however in the absence of positional data it could be nothing more than a suggestion rather than something concrete.

Furthermore, I had my own suspicions that the correlation between shot limiting and possession allowed in the final third, as outlined in part one of the paper, had a connection to what I was exploring in the papers second part in regard to defensive line spacing and positioning. From a tactical standpoint, it would make sense that teams that limit final third possession, have even lines better equipped to confront the ball higher, but, again, without that positional data, it wasn’t something that could be explored.

Since then, I have desperately sought positional data on defensive actions in order to further explore this topic. You can probably all see where this is going, but long story short, I was able to acquire 2015 positional data on defensive actions, and, with the graphical help of ASA contributor, Kevin Minkus, who created the incredible defensive action maps displayed below. I am now able to more deeply explore the relationship between shot limiting, final third possession, and where teams position their lines.

Before we get to the nifty maps, I want to briefly go over 2015 correlations between possession allowed in the final third to shots given up, because it’s extremely relevant to the tactical concepts we’ll explore with the maps.

In 2014, the correlation between shots against and possession allowed in the final third was 0.388, which was the highest correlation of the paper, for any full year— higher than possession, shots for and tackles per pass allowed.

In 2015 so far, that correlation is even higher, jumping to 0.4768.