Transcript for Shocking Admission From Football Great Bret Farve as He Was Called Back to Play
We begin with late news from a legendary athlete, brett favre, the former nfl quarterback and a 44-year-old grandfather. But there have been rumors he might make a come back and then late today, a very different and worrying headline, abc's david kerley has the very latest right now. Reporter: Over 20 years quarterback brett favre took a pounding, the last hit of his career in 2010 knocked him out. It's one of the few times i kind of went blank there for a while in my career. Just the way I guess I shrunk around on the turf. Reporter: Three years after his career ended, favre said he's frightened about the toll the game has taken. Today telling espn that he has experienced memory loss. After 20 years god only knows the toll. This was a little shocking that I couldn't remember my daughter playing youth soccer. It was just one summer, I think. Reporter: Espn looked at the science of concussions, 60 percent are head to head like a sledge hammer to the head and it only takes 15 milliseconds. That's why the nfl instituted new rules about head hits and paid out three quarters of a billion dollars to former players. Favre's admission came as his name came up as a replacement quarterback for an nfl team. It's not the first time since he retired but he has the same answer. It's flattering but there is no way I'm going to do that. Reporter: Favre, a future hall of famer is one of the names associated with the concussion problem. He has considered having tests done on his brain looking for a buildup of proteins but he says he hasn't done it yet because there isn't much treatment now even if they do find a problem. Even with the changes that the nfl has made, critics argue the game in america is still too violent.
This transcript has been automatically generated and may not be 100% accurate.