The team announced Souza's diagnosis following a 14-0 loss to the San Francisco Giants. Souza left the game in the fourth inning after diving for a ball and missing in right-center field. He kicked his legs in apparent pain while waiting for a team trainer, then walked off the field holding his arm.
Souza was acquired from the Tampa Bay Rays as part of a three-team trade last month. The 28-year-old batted .239 with 30 home runs, 76 RBIs and 16 stolen bases last season with the Rays.