Indianapolis Colts quarterback Jacoby Brissett returned to the game Sunday after a hit in the third quarter left him reaching for his head, prompting criticism from a prominent concussion expert.

Chris Nowinski, co-founder and CEO of the Massachusetts-based Concussion Legacy Foundation, posted a video of the hit on Twitter and called the NFL's concussion protocol "a fraud." Nowinski wrote that Brissett showed "the clearest concussions (sic) signs of the season."

"Helmet-to-helmet hit, holds head, then goes limp, then needs help up," he wrote. "You don't need a protocol to hold this player out for the game. Check the tape."

Brissett was not permitted to speak to the media after the game. A Colts spokesperson told reporters that he developed concussion-like symptoms after the game.

On the play in question, Brissett reached for his head after sustaining a hit and remained motionless on the field for a few seconds before being helped off by teammates. He was taken to the training tent for examination, and it appeared that backup Scott Tolzien was going to enter the game, but Brissett returned before Tolzien could take a snap.