The Emergence of Concussion Issues
Concussions in baseball occur in various situations including hit-by-pitches, collision plays, and fence crashes. For decades, NPB lacked systematic responses to concussions. In 2016, a Yomiuri Giants player continued playing immediately after being hit by a pitch, only to be diagnosed with a concussion after the game. Such cases were merely the tip of the iceberg, as the longstanding practice of allowing players to continue if they self-reported as fine persisted throughout the league. In the United States, the NFL acknowledged the causal link to chronic traumatic encephalopathy (CTE) in 2009, and MLB introduced its 7-day injured list system in 2011, rapidly advancing protective measures. A 2013 survey by the Japan Neurosurgical Society reported that approximately 30% of sports-related concussion cases returned to competition without adequate rest, strengthening the recognition within NPB that institutional reform was urgently needed.
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NPB's Concussion Special Measures
NPB officially introduced concussion special measures starting from the 2017 season. The system has three key components. First, players who receive head impacts during games can be temporarily removed at the umpire's discretion for examination by team doctors or stadium medical staff using SCAT5 (Sport Concussion Assessment Tool, 5th edition). Second, if diagnosed with a concussion, the player's active roster registration can be specially revoked with a minimum 7-day rest period, and a replacement player can be registered the same day. Third, return to play requires completion of a Graduated Return to Play (GRTP) protocol supervised by the team's medical staff. In the inaugural year of 2017, there were 8 special measure applications across both the Central and Pacific Leagues, with cumulative cases exceeding 40 through the 2022 season. Before the system's introduction, it was not uncommon for players to appear in games the day after receiving head-area hit-by-pitches, but the special measures have helped spread the awareness that resting is not a sign of weakness throughout the baseball world.
Operational Challenges
Several challenges remain in implementing concussion protocols. First, there is the issue of diagnostic consistency. While SCAT5 is an internationally standardized tool, assessment outcomes can vary depending on the examining physician's experience level. During the 2021 All-Star Game, a player who took a foul tip to the head was cleared to continue playing, only to have symptoms worsen the following day. Second, there is the player self-reporting problem. Particularly during the postseason and Climax Series, players have stronger motivation to underreport symptoms to remain in the game. During the 2019 Japan Series, a pitcher who was struck by a batted ball on the head insisted he was fine and wanted to continue, but was removed based on the team doctor's judgment. Third, there are disparities in medical infrastructure among the 12 teams. Well-funded organizations can employ dedicated neurosurgeons, while others rely on orthopedic surgeons handling concussion assessments as a secondary role, potentially creating differences in diagnostic accuracy. Since 2023, NPB has mandated concussion response training programs for all teams to standardize diagnostic criteria.
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International Trends and NPB's Future
MLB has progressively strengthened its protocol since the 2011 introduction. Starting in 2022, automatic concussion evaluations were added for pitchers hit by batted balls near the head, establishing a system that does not rely solely on player self-reporting. Korea's KBO also introduced similar special measures in 2018, reflecting a growing momentum for player protection across Asian baseball. While NPB's system matches MLB's minimum 7-day rest period, it differs in that the deployment of independent concussion spotters (certified athletic trainers) is not yet mandatory. Future priorities include stationing concussion specialists at all stadiums, establishing NPB-specific certification standards for helmet impact absorption performance, and strengthening coordination with the collision rule at home plate (introduced in 2016). In 2024, NPB and the Japanese Society of Sports Medicine jointly began revising the Guidelines for Concussion Management in Professional Baseball Players, marking a new phase in efforts to protect players' long-term brain health.