NEW YORK (AP) - The NFL is checking whether concussion protocol was properly followed Sunday when Houston Texans quarterback Tom Savage was allowed to briefly return to action after a disturbing hit in the end zone that left him with his hands quivering.

League spokesman Joe Lockhart said the NFL and the players' association "together will conduct a thorough review of the incident focused on whether the protocol was properly followed, but we're also continuing looking at the protocol to look for ways to improve and strengthen it."

Lockhart said the discovery during this investigation of any possible improvements to the concussion protocol will be quickly implemented.

The NFL's concussion protocol came under heavy criticism after it failed Savage on Sunday in Houston's 26-16 loss to the 49ers. Only after Savage briefly returned to the game did the medical crew determine the quarterback did, indeed, have a concussion and remove him from the game.