Quantifying the Effect of Performance-Enhancing Drug Use on Fastball Velocity in Major League Baseball

Since 2005, Major League Baseball (MLB) has suspended 258 players under its Drug Prevention and Treatment Program. Moreover, the Mitchell Report yielded the names of 89 alleged users of performance-enhancing drugs (PEDs). This documentation enables quantification of the impact of PEDs on player performance. Literature with this goal is limited, and has focused primarily on batters. Some authors have examined Roger Clemens, but there has been no previous work assessing the influence of PEDs on pitchers more generally. We gathered average fastball velocity from Fangraphs.com for all MLB pitchers who threw at least 10 innings in a month between 2002 and 2008 (11,860 player months). Pitchers were deemed to be PED users if they were named as such in the Mitchell Report or suspended by MLB for a positive PED test. Human growth hormone (HGH) usage was tracked separately. We modeled fastball velocity by PED and HGH usage, age, a Starter/Reliever indicator, and several control variables. Using PEDs significantly increased average fastball velocity by 1.074 MPH overall. When PED impact was allowed to vary by pitcher type (Starter/Reliever) and age, its benefits were most substantial later in a player's career. For example, at age 35, the effect of PEDs was 1.437 MPH for relievers and 0.988 MPH for starters. HGH use was significantly negatively correlated with fastball velocity. This suggests disproportional HGH use by injured players hoping to hasten their recoveries, and is consistent with frequent explanations provided in the Mitchell Report.