The team says it acted properly after the star QB appeared to stumble after a blow to the head against the Saints on Sunday.

CHARLOTTE, N.C. — With an NFL and players union investigation pending, a national concussion expert and player safety advocate says the Carolina Panthers broke protocol when quarterback Cam Newton was allowed to re-enter Sunday’s NFC wild-card game without a more extensive medical exam.

“Any loss of balance means you have to go to the locker room,” says Chris Nowinski, Ph.d, CEO of the Concussion Legacy Foundation. Nowinski sits on the NFL Players Association’s Mackey-White TBI Research Committee, a group that has been active on player safety issues.

Panthers coach Ron Rivera and interim general manager Marty Hurney both said Monday they believe the team acted properly after Newton took a big hit to the head in the fourth quarter of the 31-26 loss to the New Orleans Saints.

“We did everything the right way,” Hurney said.

Newton left for one play after Saints defensive tackle David Onyemata’s chest struck Newton’s head with about nine minutes left.

Newton walked toward the Panthers’ sideline and appeared to stumble to the turf as trainers met him a few yards from the bench area.

The stumble, Nowinski said, should have triggered sideline medical staff and other NFL-contracted concussion spotters to call for Newton to undergo an exam in the Panthers locker room.

“He went down right after getting blasted in the head. ... You have to assume concussion and that should be interpreted by loss of balance,” Nowinski said.

Another national concussion expert, Dr. Robert Cantu, said it’s not clear to him whether Newton should have gone to the locker room. Cantu is senior advisor to the NFL Head, Neck and Spine Committee.

The team said Newton was evaluated for a concussion in the medical tent on the sideline, and he was cleared to return. Newton said after the game the issue was with his eye, not his head.

The NFL and union announced changes to the protocol last month in the wake of Texans quarterback Tom Savage returning to the field after having an apparent seizure after a hit.

Among the changes was the requirement of a locker room concussion evaluation for all players “demonstrating gross or sustained vertical instability (e.g., stumbling or falling to the ground when trying to stand).”

Panthers officials reiterated Monday that Newton was following instructions from the sideline to take a knee so backup quarterback Derek Anderson could loosen up.

“He took a hit. But when he walked off and he told the trainers he got poked in the eye, then they did take him into the tent and checked him for a concussion, which he did not have,” Hurney said.

“And it was really getting poked in the eye. He took a knee because they told him to take a knee so we could get the official timeout and Derek could warm up.”

Nowinski said the NFL is right to investigate and believes the Panthers should be punished.

“They (the NFL) have to enforce it,” he said. “They have to punish groups who don’t follow the protocol.”