Boston Red Sox slugger J.D. Martinez left Thursday's game against the Kansas City Royals because of back spasms.
Martinez, serving as Boston's designated hitter, was scheduled to bat in the top of the fifth inning but was replaced by Sam Travis.
Martinez struggled with back spasms last month, missing four consecutive games. He also missed two games in April.
Martinez had doubled in his previous at-bat Thursday and scored a run on Rafael Devers' single in the third inning.
Martinez drove in 130 runs to lead the American League last season, and batted .