Two NFL players violated league protocol on dealing with concussions in last weekend's wild-card playoff games, according to a document obtained by the Associated Press.

The document was a letter sent by the NFL's head, neck and spine committee chairmen to all team doctors and trainers.

In the letter, Drs. Hunt Batjer and Richard Ellenbogen say one player re-entered the game after suffering a possible concussion and another refused to leave the sideline. Although the letter doesn't identify the players, AP does, as Green Bay tackle David Bakhtiari and New Orleans cornerback Keenan Lewis.

Bakhtiari went back into the game against San Francisco for an extra-point try, despite not being cleared to re-enter. Lewis remained on the sideline but didn't go back into a game at Philadelphia.

The doctors found "no fault" in how the teams' medical staffs handled the situations.

"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 a 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," the letter said.

No fines will be imposed for the violations, according to the AP.

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