How Swing Tilt Translates into Batted-Ball Outcomes: Pitch-Type-Specific Mediation by Bat Speed in MLB

Recent advances in Statcast bat-tracking technology enable direct measurement of swing mechanics during MLB competition, but the performance relevance of these metrics remains unclear. Using 61,220 fastball swings and 45,808 off-speed swings from the 2024 MLB season, this study examined within-batter associations among Swing Tilt, Bat Speed, and batted-ball outcomes using batter fixed effects and batter-clustered inference. For fastballs, Swing Tilt was positively associated with Bat Speed (β = 0.148) but showed negative direct associations with Hit Distance (β = −0.105) and Launch Speed (β = −0.075). Indirect associations through Bat Speed were positive for Hit Distance (0.597, 95% CI [0.540, 0.656]) and Launch Speed (0.095, [0.087, 0.104]). For off-speed pitches, direct associations were not statistically significant (β = 0.010 and 0.003), whereas indirect associations were positive for Hit Distance (0.469, [0.406, 0.534]) and Launch Speed (0.097, [0.086, 0.108]). Overall, Swing Tilt showed context-dependent associations with batted-ball performance.