Brett Favre was knocked out cold once in his 20-year career and it came on his very last snap. But the Hall of Fame quarterback knows that he suffered more than one concussion during his two decades in the NFL.

In fact, he recently told the Chicago Sun-Times that "probably 90 percent" of the tackles he endured left him concussed. And more than that, Favre, who says his health hasn't declined since he retired in 2010 is "absolutely 100 percent" concerned about his future well-being.

And while the NFL has taken measures to reduce head injuries, Favre remains an outspoken advocate for more research on the issue.

"The athlete is getting bigger . . . faster . . . stronger, I don't think that's going to change," Favre told the Sun-Times. "So the fact that we tackle and the hits are becoming more violent, I don't see how the concussions will go down. At some point, we have to look at treatment. Prevention can only go so far."

Favre, Kurt Warner, Mike Ditka and nine other current and former athletes are investors in a drug called Prevacus.

The drug is administered as a nasal spray and is recommended after diagnosis of a brain injury. Prevacus is said to reduce swelling, inflammation, oxidative stress and cell death in the brain, according to its creator, Dr. Jake VanLandingham. The drug has not been approved by the FDA.

In January, Favre told CBSSports.com's Pick-Six Podcast that he would prefer his grandsons played golf instead of football.

"I have three grandsons -- and people may wonder why a retired player would be so adamant about concussions and making the environment safer -- I don't know if they'll play football. They're eight [years], three [years] and several months old," Favre said. "What little bit I know now -- and it's more than when I played -- concussions [are] not good. And definitely not for a youth. And so, there is something out there that can make the environment safer, aside from helmets, and that is the surface. I think you have to look at the surface as an equal if not more important than the equipment you wear. ...

"I'm not going to encourage them to play. I'm not going to discourage [them]," Favre said. "But I say this to everyone who will listen: if my grandsons were to say, and they call me Paw-Paw, if they were to say 'Paw-Paw, will you be my caddy in golf, I think I'm going to do golf instead of football,' I would be much more happy, satisfied and excited by that then by them playing football.

"Every tackle I would be cringing, hoping they get up and not shaking their head and saying they got a headache. But the likelihood of that happening by them playing football is very high. So I'd much rather them choose a safer route."