On Opening Day of the 2015 season, in his first game with Boston in almost 10 years, Ramírez played left field for the first time in his career and hit two home runs (one of them a broken-bat grand slam) for a total of 5 RBI as the Red Sox routed the Philadelphia Phillies 8–0. On April 29, Ramírez hit his 10th home run of the season, joining teammate David Ortiz as the only players in Red Sox history to hit 10 home runs in the month of April. However, a few days later on May 4, Ramírez left the game against the Tampa Bay Rays in the top of the first inning after crashing into the left field wall at Fenway Park. The team announced shortly after that he had suffered a left shoulder sprain.