Study of 8,022 MLB Pitch Pairs Finds Whiff Rate More Repeatable Than Run Value

A data analyst examined Baseball Savant pitch statistics from 2017 to 2025 to determine how consistently five pitch-level metrics carry over from one MLB season to the next. Using 8,022 pitcher-and-pitch-type pairs with at least 100 pitches in both seasons, the study measured year-over-year correlations for usage rate, whiff rate, xwOBA allowed, hard-hit rate, and run value per 100 pitches. Whiff rate proved the most stable quality metric, with correlations ranging from 0.53 to 0.74 depending on sample size, while run value was the least repeatable, peaking at just 0.35 even for pitches thrown 800 or more times. All five metrics showed stronger correlations as pitch counts increased, consistent with the expectation that larger samples reduce statistical noise. The findings suggest that a single season of run value is a weak predictor of future performance, whereas whiff rate offers a more reliable signal of a pitch's true quality.