The NFL continues to investigate whether the Carolina Panthers followed proper concussion protocol after quarterback Cam Newton sustained an injury in last week's wild-card game. But a new dynamic has emerged.

Team officials have informed the league that a knee injury was partly to blame for Newton staggering to his feet and then stumbling to the ground after taking a blow to the head from New Orleans Saints defensive lineman David Onyemata, a league source informed ESPN's Adam Schefter. Newton - who argued he suffered only an eye injury, not a concussion, on the play - was evaluated in the medical tent on the sidelines and was cleared of a concussion by the team moments later.

SACK: @aces_e lookin' like the next WWE star 😱#SaintsGameday | #CARvsNO pic.twitter.com/n8KkEMJRDu— New Orleans Saints (@Saints) January 8, 2018

The NFL has interviewed Panthers officials over the phone since the incident. The league is investigating whether the team should have taken Newton to the locker room for further evaluations, as new concussion protocols stipulate.

Newton underwent an MRI on his knee on Monday, which came back negative.

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