"I'll get an MRI [Friday], so we'll figure it out,'' Siemian said after the Broncos' 25-13 win.
Siemian, who had surgery on the shoulder after the 2016 season and was held out of some of the team's offseason work, was sacked by Barkevious Mingo late in the first quarter and landed on his left arm and shoulder. Siemian immediately got up holding his left arm against his body and was examined by the Broncos' medical staff before being taken to the locker room.
Siemian, who had a sling around his arm and shoulder, said he doesn't believe Thursday's injury was related to the one from 2016.
"It's not the same thing, I don't think, so dodged a bullet on that end,'' Siemian said. "We'll see.''
Brock Osweiler replaced Siemian against the Colts. He finished the game 12-of-17 with 194 yards with two passing touchdowns. Osweiler also ran for a touchdown.
Siemian started the Broncos' first seven games but was benched after a three-interception game in an Oct. 30 loss to the Kansas City Chiefs.
Siemian was 5-of-9 passing for 67 yards with an interception against the Colts before his injury. His interception was his 10th in a road game this season. Mingo's sack was already the second of the game on Siemian.