Within a fraction of a second, it became clear that New England Patriots running back Stevan Ridley suffered a concussion during the AFC Championship (h/t Jeff Rowe) following a brutal hit by Baltimore Ravens safety Bernard Pollard.
The events leading up to the tackle, the hit itself and Ridley's reaction following the blow could be placed in a textbook on NFL concussions. And the sight of Ridley leaving the game immediately afterward did not shock anyone.
What made it obvious that Ridley suffered at least the 171st concussion this season, according to PBS' Concussion Watch?
Here is a closer look, beginning with a clip of the injury itself.