Troy Vincent recalls going back to the huddle and forgetting to look at the sideline for the play, even though it was his job to relay the signal. He mentions the days after one concussion when he couldn't remember phone numbers and kept thinking his car was running. When he sees clips of himself knocked unconscious, he cringes. "I'm not sure if we -- athletes -- know what a concussion is," said Vincent, a veteran defensive back and the president of the NFL Players Association. The NFL is taking steps to educate players on the subject and make sure they report concussions, implementing a whistle-blower system when training camps start next month. The league hopes that will ease pressure on players to take the field with a concussion.