The Kansas City Chiefs will have to battle through the rest of their divisional round game against the Buffalo Bills without one of their top defenders.
Safety Tyrann Mathieu left the game on the opening drive after attempting to tackle Bills QB Josh Allen.
The team later confirmed that Mathieu was in concussion protocol and would not return.
Mathieu was selected to his third Pro Bowl this season, his second as a member of the Chiefs.
Buffalo and Kansas City remain knotted at 7-7 in the second quarter of the game.