"I won't know until we figure out how severe it is, so, I mean, he does have a dramatic swing, there's a lot going on," Melvin said. "He creates a lot of torque, that's just who he is, but there is a concern that he's had a few days off, then we got him back in the field and had to take him out. But hopefully it's something that's manageable here pretty soon."
Without Cespedes, the A's are missing one of their hottest players. Cespedes is batting .314 in September, and he is second in the American League with 19 RBIs in the month and tied for third with six home runs.
Jacob Thorpe is an associate reporter for MLB.com.
This story was not subject to the approval of Major League Baseball or its clubs.