Former Washington Redskins running back Clinton Portis needed four months to gain clearance from a November 2009 concussion that left him struggling to regain his vision. He went on to play just five games in the rest of his NFL career.
Portis now believes he sustained more than 10 concussions in his nine seasons as an NFL player.
"The truth is I had a lot of concussions," Portis recently told Mike Freeman of CBSSports.com. "It was just the way things were at the time. I'd get hit hard and be woozy. I'd be dizzy. I'd take a play off and then go back in. Sometimes when I went back into the game, I still couldn't see straight. This happened all the time. Sometimes once or twice a game."
Not only was Portis one of the game's most powerful runners, he also was a devastating blocker. He said he "stopped counting" the number of times he played through brain trauma.
Concussions vary from Grade 1 (seeing stars) to Grade 3 (knocked out). Former San Diego Chargers linebacker Gary Plummer has estimated that he experienced 1,000 Grade 1 concussions in his career while the late Junior Seau sustained closer to 1,500 at the rate of five per game.
Although Seau battled post-career demons prior to his suicide, Portis insists he walked away from the game healthy with no known effect from his concussions.
"I have a few aches and pains," Portis said. "Nothing major. None of the, 'I can't stand up or walk' stuff. I got away from the game at the perfect time. To be 31 and retired and spending time with my kids, I love it."
Portis played the bulk of his career in the era before the NFL began cracking down on concussions. At a time when Jahvid Best can't find a doctor to green-light his return to the gridiron, it's natural to wonder if Portis' career would have been shortened had he come along a decade later.
Follow Chris Wesseling on Twitter @ChrisWesseling.