CLEVELAND (AP) — Boston Red Sox first baseman Triston Casas is out indefinitely after breaking a rib on his left side while taking a hard swing in Saturday’s game at Pittsburgh.

Casas, who had been placed on the injury list with a strain, underwent tests in Boston that revealed the fracture. Manager Alex Cora said there is no timetable on when the 24-year-old will be back.

“He’ll be out for a while,” Cora said Tuesday before the Red Sox opened a three-game series at Progressive Field. “We just have to be patient. It has to heal on its own, so we just have to be patient.”

Cora expects Casas, who was batting .244 with six homers and 10 RBIs, to return at some point this season. Cora said Casas told him that his rib was bothering him last week in a series against the Guardians.

On Saturday, Casas injured himself while fouling off a two-strike pitch in the first inning. He drew a walk and was replaced defensively in the next half inning.