Playing for the Minnesota Vikings in December 2010, Favre's career came to an end when his head hit the frozen turf at Minneapolis' TCF Bank Stadium.Follow @cnnsportAnd ahead of Super Bowl LII — the Philadelphia Eagles and the New England Patriots play Sunday — Favre says the only way to avoid injury in football is to not play the game at all."Well I think first of all, how do you make the game safer? You don't play. Is that gonna happen?" Favre told CNN's Christiane Amanpour.Chronic traumatic encephalopathy, known as CTE, was found in 99% of deceased NFL players' brains that were donated to scientific research, according to a study published in the medical journal JAMA in July.The neurodegenerative brain disease can be found in individuals who have been exposed to repeated head trauma.Dr. Bennet Omalu is credited with first discovering CTE in professional football players and he told Amanpour that he'd stopped watching football five years ago."As a physician and brain expert, in every play in football, there's a blow to the head. A paper recently came out from Stanford that showed in just one game, a player is exposed to 50 to 60 violent blows to the head."Some are like a car traveling at 30 mph slamming into a brick wall. So we need to realize it's not about the concussions. "You could play just one game on Super Bowl Sunday — after just one game, many players have suffered irreparable brain damage. All you need is one violent blow. What goes through my mind: where will these players be in 20 years?"According to Favre, NFL players are going to get "bigger, faster, stronger." "And so the contacts are going to be much more violent," added Favre. "And so concussions will continue to be a serious issue. There's only so much that helmets can do. So we'll look at it from a treatment standpoint. And the only other option is not to play."I think we have started the ball rolling if you will in the right direction, by instituting a concussion protocol."It's a neurologist who's at every game, and if he thinks you have a concussion, you're supposed to be removed. That's better than it was years ago."When asked about Favre's comments, NFL commissioner Roger Goodell told a media conference Wednesday: "I would tell you this: this has been a major focus for us in trying to make our game safer at our level and all the way through every level of football."The game of football is much safer than when I played it, but that's part of our responsibility and we take that seriously and it's something we'll continue to focus on.READ: Super Bowl LII weather forecast: Freaking freezingREAD: Quarterback Foles' Super Bowl dreamREAD: Eagles star dons wrestling mask
'Writing on the wall'
Hall of Fame quarterback Favre has been working on a documentary, "Shocked: The Hidden Factor in the Sports Concussion Crisis," taking the role of executive producer.He recalled his final day of action back in 2010 when he sustained concussion and the moment he knew it was the right time to call it a day."It was extremely cold, the field was icy, and very hard," said Favre, who was playing for the Minnesota Vikings at the time."I was closing in on 41 years old. I know there's never a good time to have concussion, and I thought after this particular play, when for lack of a better term the cobwebs had cleared."As as I was standing on the sidelines, I thought, you know, if there was ever writing on the wall, this is it."Again, concussions, there's never a good time to have them. But at 40 years old, if I question whether or not I should come back and play, at that point I knew it was time to leave the game. "I'll be honest, that was eight years ago, and at that time I didn't thing it was as serious, generally speaking, as it is today. But I did know it was time to step away from the game."