The NFL Players Association plans to initiate a review of whether the Miami Dolphins followed the league's concussion protocol when allowing quarterback Tua Tagovailoa to return to Sunday's game, ESPN and NFL Network reported.

Tagovailoa left the game against the visiting Buffalo Bills with 2:19 left in the second quarter. Bills linebacker Matt Milano shoved him to the ground for a roughing-the-passer penalty, and the back of Tagovailoa's head hit the turf. He was wobbly and stumbled to the ground while running off under his own power.

Tagovailoa ended up returning for the Dolphins' first possession of the third quarter.

After the game, the Alabama product said he hurt his back on a quarterback sneak earlier in the game.

"But for the most part, I'm good," Tagovailoa said. "Passed whatever concussion protocol they had."

Tagovailoa was able to stay in for the rest of the game. The Dolphins held off the Bills 21-19 to move to 3-0 and into sole possession of first place in the AFC East.

As part of the collective bargaining agreement, "the NFLPA, the NFL Management Council or any player involved in an alleged failure by a club employee or other member of a club's medical staff to follow any of the mandatory steps required by the NFL's Concussion Checklist shall each have the right (independently or collectively) to bring forward a complaint about such alleged failure to the Representatives, which complaint shall be submitted in writing."

The executive director of the NFLPA and the NFL's deputy general counsel for labor are required to resolve the complaint no later than three weeks following its filing, which can result in disciplining a team if appropriate. If the sides do not agree on a resolution after three weeks, it can go to an impartial arbitrator.