NWSL Defensive Play Part II
An early exploration using the data collection effort from the WoSo Stats team and an effort to create a user friendly interactive tool.
If you have not read NWSL Defensive Play, the only thing you need to remember is the following: I love defense. I love it. I think it is absolutely beautiful to watch this dynamic within the backline and even the exchange between the defenders and midfielders. From a photography standpoint, those who follow me know this is my favorite thing to capture so I figure, it must also have some beautiful stories to tell through the data, right? So let’s explore!
What type of midfielder are you?
In NWSL Defensive Play, I defined two different actions — conservative and aggressive, or ball defending and player defending. Originally, this data was presented such that you could see every single player in the league and it honestly looked like utter nonsense unless you had a specific player you wanted to see. Thus, instead, we focused on player position by team. For now, forget the teams for the second and just look at the three clusters — forwards in orange, midfielders in red, and defenders in blue.
Conservative action is on the y-axis and aggressive action is on the x-axis so for those not familiar, the higher up you are, the more conservative while the more to the right you are, the more aggressive. The immediate thing that stands out — defenders and forwards are compact in their clusters while midfielders are all over the place in aggressive action. Who are these midfielders with insane aggression? It is pretty easy to guess — Portland Thorns!
Now, there are a few more interesting stories to tell with this before moving on. First, Chicago Red Stars have a midfield that is the most conservative and third most aggressive. Meanwhile, Washington Spirit midfield and forwards seem to not take too much defensive action at all. Now this latter statement might have a logical explanation — Spirit kept possession and did not need to take so much defensive action. One thing we do know, their defenders are the most conservative and make the least mistakes (size of circle) at least in the first half of the season. Now that we have established this idea of conservative and aggressive action by position, let’s add another layer — location.
The Symmetry of Defensive Action and Pressure
Defense in the defensive third — this is the most obvious statement in the world but what type of defense is the question! Again, remember that higher position means more conservative action and within each location section (labeled on the top), the right side is more aggressive. Lastly, size of circle means more defensive mistakes.
Hopefully this is clear because the first thing I want to draw your attention to are the defenders. You can literally see their conservative action increase up until the defensive third and then taper off because they have now reached a region ruled by the goalkeepers. If you are wondering who the outliers are — it is Seattle Reign! Now let’s take a closer look at the midfielders and forwards.
As the initial data illustrated, forwards do not do as much defensive action. Midfielders tend to increase but not as much as defenders and they are specifically more aggressive when they take actions. However, this begs another question: if not action, then what about defensive pressure? So instead of conservative and defensive action, we will now compare pressure per game (the higher you are) to total action per game.
All of a sudden, we have a completely different story because the midfielders and forwards are more likely to pressure their opponents into making a mistake rather than take a physical defensive action. You can even identify which teams are rather symmetric in terms of trading responsibilities between position and location. However, it become pretty apparently that data like this needed a better representation than a scatter plot so instead, we decided to finally implement a heat map. Now please note, this is still in development and in fact, we accidentally marked the right side as left and the left side as right! This explains my terrible driving skills…regardless, here is an illustration of Western New York Flash on the left and Washington Spirit on the right for defensive pressure. Flash pressure more but more specifically have a region defined in the midfield that is bigger compared to the Spirit.
We can compare this to conservative defensive action and get a completely different story. Washington Spirit’s right side (remember it is on the left here) has a lot of ball defending activity (former captain Ali Krieger’s regime). In comparison, much of that conservative action for Western New York Flash is in the central defensive third or 18 (yd box). Different teams use different tactics to defend and you can even get player specific if you wanted.
Now, if you liked what you saw above with the heatmaps, here comes the shameless but necessary self-promotion part of this article. As a student at University of Washington working with a great group of individuals to create this NWSL Data Tool for class, we need local user testers in a few weeks. This means anyone in Seattle who can come to University of Washington or Kirkland Library (as an alternative location on weekends only), we need your help! You will get exclusive first time access to this tool (with so much more included) before we make it public to everyone and you can help us make it better and find mistakes! Please contact ntaparia@uw.edu if you are interested.
Add your thoughts, observations, and questions below. Make sure to check outWoSo Stats on Twitter, how you can help, the stats database, definitions of these stats, and some visualizations courtesy of WoSo Stats. The visualization presented here are from an exploratory analysis done by my University of Washington group (data scientists and user engineers) and everything will go public after user testing!
