Overview
The Rookie of the Year award honors the best first-year player in each league. NPB eligibility requires being within five years of joining a team, with pitchers limited to 30 innings and batters to 60 plate appearances in prior seasons. High school draftees sometimes win after several years in the farm system, while college and corporate league players tend to win more readily as immediate contributors. Hideo Nomo won both Rookie of the Year and MVP in 1990 with 18 wins. In 2022, reliever Yoshinobu Mizukami (Seibu) took the Pacific League award, while Roki Sasaki, despite throwing a perfect game that season, was ineligible because his prior-year innings exceeded the limit. The award is considered a gateway to stardom, though the sophomore slump remains a well-known phenomenon.