Richardson scored a rushing touchdown on each of the Colts' first two drives in Sunday's win over Houston but was ruled out in the second quarter due to a concussion.
The dual-threat quarterback was believed to have suffered the concussion after taking a hit in the end zone following his second score. His head slammed to the turf, but Richardson stayed in the game the following drive. The rookie later self-reported symptoms and was pulled from the contest.
Richardson's status for Sunday's game against Baltimore won't be clear until later in the week.
The No. 4 overall pick has looked dynamic in his first two starts, rushing for three touchdowns while throwing for 279 yards with a TD and an interception in under six quarters of play. However, injuries are already becoming a concern as Richardson has ended both games on the sideline.
"You're always concerned," Colts owner Jim Irsay said after Sunday's game, per ESPN.com. "The first game, he banged up the knee, but it was OK, just a contusion. This game, banging the head. I think it's just something where he's got to protect himself. He's a big, physical guy. Obviously, he can run the football, and guys do a lot of running now at that position. And, so I think self-protection is an issue."