Mahomes's body (particularly his left fist) with the OP's provided replay — watch the body & hand right at the moment the defender's hand makes contact with his chin. He hits the chin w an open hand, but it's right at the solid part of the hand at the base of the thumb. You catch someone just right with that part of your hand it can be almost as bad as hitting them with a closed fist.

He was concussed, but it was with a simple chin-shot. His brain & spine are likely fine. If the NFL weren't so sensitive about these things (& rightly so), I bet he woulda returned yesterday after a lil rest. And been just fine.