The document was a letter sent by the chairmen of the NFL's head, neck and spine committee to all team doctors and trainers.
In the letter, Drs. Hunt Batjer and Richard Ellenbogen say one player re-entered a game after suffering a possible concussion and another refused to leave the sideline. Although the letter doesn't identify the players, the AP said they were 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 the 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.
Indianapolis Colts receiver Darrius Heyward-Bey will not play in Saturday's playoff game at New England. Heyward-Bey did not practice all week because of a hamstring injury. Coach Chuck Pagano said Heyward-Bey was expected to miss at least a week; the team had signed former New England receiver Deion Branch to help fill the void.
Smith hopes to play
Carolina Panthers wide receiver Steve Smith said his left knee feels "fine" and hopes to be ready to play Sunday against San Francisco in an NFC divisional playoff game at Charlotte, N.C. "I will be all right," Smith said after Friday's practice. "I should be OK."
San Diego center Nick Hardwick was cleared to work out five days after sustaining a concussion and was a limited participant in practice. Hardwick, injured last Sunday in a wild-card victory at Cincinnati, was listed as questionable for Sunday's divisional playoff game at Denver.
A jury has been seated for the trial of former Dallas Cowboys player Josh Brent, who is charged with intoxication manslaughter in the death of practice squad player Jerry Brown in a drunken-driving wreck in December 2012.
Tampa Bay hired former All-Pro cornerback Gill Byrd, 52, as their cornerbacks coach.
Oakland re-signed offensive line coach Tony Sparano to a two-year contract.