Sep 30 2008

Getting Defensive for the 2008-2009 Regular Season

Now that I have a theoretical model for the probability of winning a basketball game, my goal is to collect data that will help make a useful practical model for the probability of winning a basketball game.

Existing Data

There is a lot of existing data to examine for contribution to a useful practical model for the probability of winning a basketball game. Not only that, but I expect a lot of this data to be useful. That said, this data set is far from complete with respect to its representation of the game of basketball. My goal is to add a small supplement to what the league is currently collecting to aid in understanding.

As of now, the largest need for improved data collection is with respect to defense. Therefore, this is the area that I will be focusing my data collection efforts on.

My Playoff Experiment

For the 2008 playoffs, I experimented with tracking a lot of data. Thanks in large part to the theoretical model and useful input from the analytic community, I will be focusing my efforts on collecting data that will have a direct impact on a practical model for the probability of winning a basketball game. Therefore, while some of the data I was collecting would be nice to have, this defensive data is the most important for the model I want to build.

Tracking Defenders

Although things like potential assists and pick assists are useful to know, they really only impact the defensive state a player is facing when they take a shot. This means my focus is on tracking this defensive state instead of trying to keep track of the numerous ways teammates help create spacing on offense.

The Importance of Defensive State

Although this may seem fairly basic, I feel strongly that tracking defenders that contest shots will add a lot to existing data.

Gaining more insight into team defense, especially as it relates to players and strategy, should prove to be worthwhile. Also, the goal is to use some statistical techniques to gain insight into defense without having actually tracked the data. This means we will be able to use things like play-by-play approximate these defensive states based on the sample of data that actually gets collected.

Interested In Tracking Data?

I can’t track every game. I would like to, but it’s not feasible for me. If I tried, numerous bad things would happen to me. My wife would leave me, my dogs would go hungry, and I’d fail out of school. Clearly this is not the optimal way to spend my time.

That said, I plan on making the data collection process as painless as possible to encourage others to help. Therefore, if you have a DVR and would like to help collect this defensive data, please e-mail me at:

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1 Comments on this post


  1. Examining Defense: Defensive Four Factors wrote:

    […] at the end of September, I made a commitment to get more defensive for this season. To achieve this goal, I’ve been archiving a bunch of NBA games for […]

    February 22nd, 2009 at 1:52 am