Los Angeles Dodgers’ starter Roki Sasaki pitches against the Chicago Cubs during the MLB Tokyo Series 2025 at Tokyo Dome on March 19, 2025. (Mainichi/Kenji Ikai)


The right shoulder impingement that landed Los Angeles Dodgers pitcher Roki Sasaki on the injured list May 13 is the same as an injury the 23-year-old suffered last season with Nippon Professional Baseball’s Chiba Lotte Marines, baseball sources have revealed.


According to these sources, Sasaki first experienced pain in his throwing shoulder during the first half of last season, his fifth as a professional. Medical examinations at the time produced the same diagnosis — impingement.


Sasaki reportedly complained that the pain occurred after pitching motions, saying his right shoulder “would hurt whenever I used it.” However, medical imaging revealed no abnormalities, forcing the team to depend significantly on the pitcher’s personal assessment of his condition.


Due to what the Marines officially classified as “poor condition in the right arm,” Sasaki missed nearly two months from June last season. When symptoms flared up, Sasaki managed his condition by spacing out his pitching appearances or halting throwing until the pain subsided.


Despite the lingering shoulder concerns, Sasaki posted a career-best performance in his final Japanese season, recording 10 wins and five losses in 18 games, facilitating his high-profile move to the Dodgers.


According to Dr. Tetsuya Yamazaki, head of the sports orthopedics department at Yokohama Minami Kyousai Hospital and a prominent expert on professional baseball players’ shoulder injuries, impingement often develops from collisions between the acromion — the upper outer portion of the scapula — and the rotator cuff muscles. It can also occur within the joint due to contact between the glenoid labrum and the rotator cuff tendons.


Before Sasaki’s MLB transfer, the Chiba Lotte Marines reportedly provided detailed medical and injury records, including information about his right shoulder issues, to interested MLB clubs during negotiations.


(Japanese original by Koichi Ogino, Osaka Sports News Department; and Yu Kishimoto, Tokyo Sports News Department)