HOUSTON -- Indianapolis Colts quarterback Anthony Richardson was diagnosed with a concussion and ruled out for the remainder of Sunday's game against the Houston Texans, the team announced.

Richardson appeared to hit the back of his head on the turf early in the first quarter on a 15-yard touchdown run off the right side. He remained in the game for two more Colts possessions -- during which he did not take any obvious hits -- but was later taken to the medical tent and eventually the locker room for further evaluation.

The Colts went three-and-out on both possessions after Richardson was hit on the touchdown run, although it remains unclear whether that was the hit that caused the concussion. Richardson was officially ruled out late in the second quarter, giving way to Gardner Minshew.

In addition to Richardson, Colts starting center Ryan Kelly was also ruled out with a concussion in the second half of Sunday's game.

The injury risk for Richardson while running the football has been a topic of late, given his running proficiency and the Colts' proclivity to use him as a runner.

"I think there is a fine line, but I think if you go look at it statistically, most quarterbacks if they do get hurt -- if you look at all the numbers -- it's within the pocket more than anything," Colts coach Shane Steichen said earlier this week. "Again, we have those conversations weekly about when to be smart."

Richardson rushed for touchdowns on both of the Colts' first two series in the game.