Predictors of Fielding Performance in Professional Baseball Players

The ultimate zone-rating extrapolation (UZR/150) rates fielding performance by runs saved or cost within a zone of responsibility in comparison with the league average (150 games) for a position. Spring-training anthropometric and performance measures have been previously related to hitting performance; however, their relationships with fielding performance measures are unknown. Purpose: To examine the relationship between anthropometric and performance measurements on fielding performance in professional baseball players. Methods: Body mass, lean body mass (LBM), grip strength, 10-yd sprint, proagility, and vertical-jump mean (VJMP) and peak power (VJPP) were collected during spring training over the course of 5 seasons (2007-2011) for professional corner infielders (CI; n=17, fielding opportunities=420.7 +/- 307.1), middle infielders (MI; n=14, fielding opportunities=497.3 +/- 259.1), and outfielders (OF; n=16, fielding opportunities=227.9 +/- 70.9). The relationships between these data and regular-season (100-opportunity minimum) fielding statistics were examined using Pearson correlation coefficients, while stepwise regression identified the single best predictor of UZR/150. Results: Significant correlations (P \u3c .05) were observed between UZR/150 and body mass (r=.364), LBM (r=.396), VJPP (r=.397), and VJMP (r=.405). Of these variables, stepwise regression indicated VJMP (R=.405, SEE=14.441, P=.005) as the single best predictor for all players, although the addition of proagility performance strengthened (R=.496, SEE=13.865, P=.002) predictive ability by 8.3%. The best predictor for UZR/150 was body mass for CI (R=.519, SEE=15.364, P=.033) and MI (R=.672, SEE=12.331, P=.009), while proagility time was the best predictor for OF (R=.514, SEE=8.850, P=.042). Conclusions: Spring-training measurements of VJMP and proagility time may predict the defensive run value of a player over the course of a professional baseball season