Richardson was escorted to the locker room early in the second quarter as the Colts defense was on the field. Indianapolis held a 14-7 lead upon Richardson's exit.
Gardner Minshew entered the game for Richardson once the Colts regained possession, and the veteran backup led a six-play, 76-yard drive that ended with running back Zack Moss celebrating in the end zone. Minshew completed both of his pass attempts (51 yards) on the scoring drive and finished the game 19 of 23 for 171 yards and one touchdown.
The rookie did appear to hit the back of his head on the turf after getting hit on his 15-yard TD run midway through the first quarter, and Colts head coach Shane Steichen told reporters after the game that he believed the injury occurred on that run, per the Indy Star.
Richardson remained in the game for the Colts' next possession after his TD run, but that drive was a short-lived three-and-out.
Steichen told reporters that Richardson self-reported his symptoms, per the Star.
It's an unfortunate end to what was shaping up to be an eye-opening performance from Richardson, who scored the first two TDs of the game. Richardson's day ended with 56 passing yards (6 of 10) and 35 yards rushing.
Richardson missed the final three plays of his first NFL start last week due to what was described as knee soreness, but he did not appear on Week 2's injury report.