The Red Sox provided few details on Jacoby Ellsbury's injury after Friday's win over the Rays. Manager Bobby Valentine said the center fielder was "in a lot of pain" after Reid Brignac landed on his right shoulder in the bottom of the fourth inning.
Third baseman Kevin Youkilis said Ellsbury told teammates he "felt something move" in his shoulder.
The best-case scenario would be a slight dislocation or separation that would heal without surgery. The worst case would be a broken bone or ligament damage. Ellsbury was taken to Massachusetts General Hospital for tests.
Valentine also said he was preparing for a player to be called up from the minors before Saturday's game.
The Red Sox have Che-Hsuan Lin on the 40-man roster. But he has no major league experience. Jason Repko, who has 355 games with the Dodgers and Twins, is on the Pawtucket roster. He was one of the last cuts in camp.