The NFL Players Association has told the NFL it wants to initiate a review of the league's concussion protocols following Miami Dolphins quarterback Tua Tagovailoa's return to Sunday's game against the Buffalo Bills, a league source told ESPN's Adam Schefter.

Tagovailoa left the contest after hitting the ground hard late in the first half, and the team announced at halftime he was questionable to return with a head injury. He completed an 8-yard pass to Jaylen Waddle after scrambling out of the pocket, and Bills linebacker Matt Milano pushed him following the throw. The quarterback stumbled backward and hit his head on the ground when he landed; Milano was flagged for roughing the passer.

Tagovailoa was slow to get up and fell as he tried to walk back to the huddle; he was escorted to the locker room shortly thereafter. According to the NFL's concussion protocol, a player must be removed from a game and evaluated on the sideline if he exhibits any concussion symptoms.

The protocol's sideline concussion assessment involves a six-step process that tests the player for any "no-go" signs, a video review of the play, a review of concussion signs and symptoms, an inquiry regarding the history of the event, all Maddocks questions and a focused neurological exam. If any element of the sideline assessment comes back positive or inconclusive, the player must be taken to the locker room for a full comprehensive review, accompanied by the team's best-suited physician and an unaffiliated neurological consultant.