Colts left guard Donald Thomas limped off the field and toward the locker room late in Wednesday's afternoon practice.
He did not return.
Afterward, team spokesman Avis Roper told reporters that doctors weren't sure what the injury was. Thomas appeared to injure his right leg during a team drill when he ended up on the ground. He got up, limped behind the team, tried to walk it off and put both of his hands on his head before leaving the playing field.
Last season, Thomas missed all but two games with a torn right quad and a torn biceps.
Receiver T.Y. Hilton also sat out the end of practice after jamming a finger on his right hand. Tight end Dwayne Allen was held out of practice for precautionary reasons.
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