Changes in pitch tempo and command-related pitching indicators during concurrent pitch clock and automated ball-strike system implementation in the KBO league

This study examined changes in pitch tempo, pitching-performance indicators, and hit-by-pitch (HBP) patterns across the 2024–2025 Korea Baseball Organization (KBO) rule-change transition, during which the pitch clock and Automated Ball-Strike System (ABS) were introduced concurrently. Official KBO game records and pitch-by-pitch event records, together with pitch-tracking data obtained from the Naver Sports relay API, were analyzed for the 2022–2025 seasons. Independent-samples t-tests, binary logistic regression, and chi-square tests were performed. Across the rule-change transition, pitch tempo decreased significantly from 34.27 ± 2.92 s to 24.11 ± 4.96 s (p < .001), with a very large effect size. HBP and wild pitch rates increased significantly, although both effects were small. In the post-transition period, pitches per inning and pitch tempo were significantly associated with HBP occurrence, whereas no significant predictors were identified in the pre-transition period. The distribution of HBP body regions also changed significantly, with a greater proportion of events involving the face and upper body after the transition. These findings indicate that the combined rule-change transition was associated with substantial changes in pitch tempo and modest changes in selected pitching-performance indicators and HBP patterns. Because the pitch clock and ABS were introduced concurrently, their independent contributions cannot be determined from the present observational design. A descriptive 2015–2025 trend analysis showed that the 2024–2025 league-wide HBP counts and HBP frequencies per 1000 batters faced remained within the historical range following a relatively low 2022–2023 baseline. Accordingly, the apparent post-transition increase in HBP cannot be distinguished from regression to the mean.