Roegele: Basic Pitch F/X park effects

From SABR member Jon Roegele at Beyond the Box Score on February 5, 2013:

In my recent work looking at characteristics of pitchers leading up to Tommy John surgery, I arrived at a point where the next logical step was to investigate pitch release points. As no readily available leaderboard is available for these metrics as far as I know, I had to go exploring myself inside the Pitch F/X database.

Pitch F/X data became publicly available for the first time in 2007. Since that time, the system has been gradually improved. While this is fairly common knowledge, nothing drives the point home more than getting your hands dirty and working with the raw data. One of the first things that became apparent to me is that the pitch characteristics reported by Pitch F/X around the league have become much more consistent since its inception. Consider the average variance in release points for all pitches by year as an example.


A similar trend can be seen in variance of pitch velocities. As it does not seem too plausible that pitchers as a group have dramatically developed more repeatable deliveries over the past five years, the tighter variance over time demonstrates an improvement in the consistency of the Pitch F/X setups from stadium to stadium.

Despite improving on an already technically amazingly accurate system, there still appear to be systematic effects introduced in the Pitch F/X systems depending on the home park. That said, what I will present today is one of the most basic approaches to looking at park effects, and other confounding factors will be contributing to the observed differences. I'll touch on at least some of these other factors toward the end of the article.

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This page was last updated February 5, 2013 at 11:40 am MST.