Simultaneous Estimation of Ballpark Effects and Team Defense Using Total Bases Residuals

TL;DR

This paper introduces a new, interpretable framework using Total Bases Residuals to simultaneously estimate ballpark effects and team defense in baseball, leveraging Statcast data from 2015-2024.

Contribution

It presents a novel regression-based method to separate and estimate ballpark and defensive effects from batted-ball data, improving upon existing metrics.

Findings

Estimates differ from official MLB metrics but show consistent performance patterns.

The approach aligns with recent changes in baseball strategies and rules.

Introduces a standardized index for cross-team and season comparisons.

Abstract

Estimating ballpark effects and team defense in baseball is challenging because batted-ball outcomes are influenced by multiple factors, including contact quality, ballpark environment, defensive performance, and random variation. In this study, we propose a simple and interpretable framework based on Total Bases Residuals (TBR). Using Statcast data from 2015 to 2024, we construct expected total bases conditional on exit velocity and launch angle, and define residuals relative to this baseline. These residuals allow us to separate the effects of ballpark environment and team defense and to estimate them simultaneously within a unified regression framework. Our results show that, when our estimates differ from official MLB metrics, the differences can be explained by consistent patterns in home and away performance for both teams and their opponents, providing empirical support for our approach. Similar patterns are also observed in comparisons with existing defensive metrics. The results also suggest changes in league-wide outcomes and are broadly consistent with developments in the game, including the increased use of data-driven positioning, the restriction on defensive shifts, and possible changes in the physical properties of the baseball. We further introduce a standardized index that facilitates comparison across teams, ballparks, and seasons by expressing effects in units of standard deviation.