During last weekend's wild-card games, Packers tackle David Bakhtiari and Saints cornerback Keenan Lewis both suffered concussions, and both players subsequently violated the league's concussion protocol, according to the Associated Press.

In a letter sent by the NFL's head, neck and spine committee chairmen, Dr. Hunt Batjer and Dr. Richard Ellenbogen -- and obtained by the AP -- one player re-entered the game and another refused to leave the sidelines. The AP identified the former as Bakhtiari and the latter as Lewis.

"On two occasions last weekend, and contrary to the advice of the team medical staffs, players who had been diagnosed with a concussion and therefore declared ineligible for play nonetheless refused to leave the sidelines as required by league concussion protocols," the letter said. "In one case, the player went back onto the field for one play before being removed from the game.

"We emphasize that we find no fault in how the team medical staffs conducted themselves last weekend. If a player refuses to follow your advice and leave the sidelines after being diagnosed with a concussion, we recommend that the head athletic trainer seek assistance from the player's position coach (or another member of the coaching staff) or from another team official to remove the player from the sidelines as soon as possible."

According to protocol, concussed players are supposed to be taken to the locker room.