Friday, November 16, 2018

Introducing Pass Zone Rating

During the international break times I like to take some time away from the daily grind of creating content and work on more research focused work. During this international break I wanted to take some time to work on using the pitch zones that I have in my database.

When I created the pitch zones, I had five zones across the width of the pitch and ten across the length.



One of the things that I always found interesting with these zones is looking at the different passing statistics for each zone.

So I thought it would be interesting to take the zones and use that as the basis for a way to measure passing skills. The idea for this is sort of similar to the defensive statistic Ultimate Zone Rating (UZR) from baseball.

To do this I went to my Premier League stats database that has data for the current season going back to 2015-16. There are a total of 1,333,739 passes that this is based on. I then took each zone and looked at the pass completion percentage based on which third it ended up in (Defensive third, Mid third or Final third), the length of the pass (less than 15 yards short, greater than 35 long, anything else medium) and finally the direction of the pass (forward, backward or square).

As my database expands even further it would be nice to be able to get even more granular with the different buckets but I think right now this works well. There is an average of 1,863 passes in each bucket and a median of 942 passes which I think makes things for a fairly robust sample for most buckets. For the zones with less than 100 passes, I used the average completions for the neighboring zones to make things more robust.

After setting the baseline for the completion percentages for each zone for each type of pass I then took that and called it "Expected Pass%" and compared that the outcome of each pass. Pass Zone Rating equals pass outcome (0 or 1) minus the expected pass completion. A completed pass will have a positive value and a missed pass will have a negative value.

Here is the top 15 in the Pass Zone Rating for this season:
The next thing that I did was look at the Pass Zone Rating and used Passing Value Added to take the expected vs actual passing and the value each pass was worth. For this, I took the passing value added and multiplied by the Pass Zone Rating and I called this Pass Zone Rating Plus.

Here is the top 15 this season in this stat:
What stands out is that there are some players that don't rate well on Pass Zone Rating but do well in this statistic. I think that is because while they don't complete a lot of passes, they do complete high value passes at a high rate.

You'll also notice on the far right there is a PZR per 1,000, I created that to normalize everyone to 1,000 passes so that people with more passes don't emerge as the leaders from accumulating a lot of easy passes.

This is a work in progress still but it is available for the 2018-19 season to Patreon Subscribers.