"I knew something wasn't right, right away," Siemian said. "It wasn't fun."
Siemian, who underwent surgery on the non-throwing shoulder in January, had completed five of nine passes for 67 yards before leaving. He also threw an interception.
The third-year quarterback was injured after being tackled by Colts linebacker Barkevious Mingo while scrambling out of the pocket. He appeared to land awkwardly on his shoulder and was holding his hand and favoring his left arm while being examined by medical trainers on the sideline. He then was carted off to the locker room.