Tuesday 13 December 2016

Blocks Away.

I've written before about a side's ability to block shots, the latest post was here and Burnley's large number of blocks in the Premier League to date has attracted the attention of Twitter.

Blocked shots may be examined in the same way that expected goals may be calculated from modelled historical data.

I have used Opta data that is the raw building block to power Timeform's InfogoApp to model the expected blocks a side may make based on a variety of variables, most notably how central a shot or header is taken from.

The model was built using data from previous seasons and used to predict blocks in the 2016/17 season to date. It adequately passed a variety of goodness of fit tests on the out of sample data.

I have looked at both the number of goal attempts that are blocked by a side, as well as the number of their own attempts that are blocked. So each side has been examined from an attacking and defensive viewpoint.

             Expected and actual Blocks in the 2016/17 Premier League After Matchday 13.

As you'd expect teams either over or under perform compared to the most likely number of blocks based on an average team model.

After 13 games, Liverpool had 78 of their own shots blocked compared to an expected baseline of 73. An under performance, but not really suggestive of anything other than simple variance.

It's slightly less easy to dismiss Sunderland's 48 blocked shots compared to an expected value of just 33. The chances that an average team takes Sunderland's attempts and sees at least 48 of them blocked is less than 1 in 200.

A simulation of all of Sunderland's goal attempts to week 13 produces the above distribution and likelihood of those attempts being blocked. Sunderland's actual block count or above can just be seen at the extreme right of the plot.

On the defensive side of the ball, the Puliser Prize for blocking in the face of adversity, surprisingly doesn't go to his current side, WBA, but Everton.

58 blocks compared to a tactically neutral expectation of just 45 and a 1 in 100 likelihood, hints at some degree of intent.

And Burnley, as they home in on a ton? 89 is a lot, but compared to an expectation of 80, it is their hospitality in allowing teams to shoot that has raised the bar as much as a tactically adepted blocking scheme.

An average side would equal or better 89 blocks after 13 games, given the shots allowed around 14% of the time.

No comments:

Post a Comment