Impact of the second‑contact rule change on Setter performance, referee home advantage, and rally dynamics in NCAA volleyball.

Purpose: This study evaluates the impact of the NCAA's 2024-25 rule change eliminating most ball-handling error (BHE) calls on second contacts directed to a teammate, testing its effects on overall BHE frequency, setter-specific risk, home-court asymmetry, and rally continuity.

Methods: Using a stable panel of 33,220 matches spanning the 2023-24 and 2024-25 seasons (over 5.2 million rallies), we fitted interrupted time-series and difference-in-differences regressions - with match fixed effects and cluster-robust SEs - to estimate post-rule changes in BHE/point, Setter vs non-Setter rates, visitor - home BHE gaps, and attacks-per-rally as a rally length measure.

Results: Model-estimated effects show a Setter shift from committing 0.0016 more BHE/point than all other positions combined to 0.0003 fewer, a shrinkage of the visitor - home BHE gap by 0.000384 BHE/point, and an increase of +0.0152 attacks/point in rally length, while non-setter BHE declined more modestly and scoring balance remained unchanged.

Conclusions: The rule change curtailed discretionary referee calls, markedly reduced Setter ball-handling infractions - the position most vulnerable before the change - and modestly extended rally continuity, while scoring distributions remained broadly similar to 2023-24.