Overview
Umpires are the official arbiters of all rule applications and judgments during a game. NPB regular-season games use a four-umpire crew (one plate umpire and three base umpires), expanding to six for the Japan Series and Climax Series with two outfield umpires added. The plate umpire's strike zone consistency fundamentally shapes game quality. NPB employs approximately 60 umpires split between the Central and Pacific Leagues, recruited through the NPB Umpire School followed by apprentice training. The introduction of replay review has improved accuracy on close plays, though the time required has sparked debate about game pace. Tracking technology now quantifies plate umpire accuracy, fueling discussion about automated ball-strike systems (robot umpires) as a potential future development.