I wonder how many of these players were less than honest with those taking care of them in order to get back on the field. Nobody is talking about that. Up until a few years ago, there was no way to physically test for a concussion. You were simply going by what the player tells you they are experiencing. So while it was obvious to see a player take a big hit and suffer immediate and obvious symptoms, the guidelines when these players played was that if the symptoms cleared within 15 minutes, they were able to return to play. These guidelines have since been changed. Google "Zurich Consensus Statement" to see how concussions are now handled.