Add Brett Favre to the list of former NFL players with growing concerns over past concussions, brain damage, and the possibility of CTE.

While appearing on Megan Kelly Today on Thursday, Favre theorized that he probably suffered way more concussions than the “three or four” officially diagnosed ones throughout his NFL career.

“When you have ringing of the ears, seeing stars, that is a concussion,” Favre said, according to Richard Ryman of USA TODAY. “If that is a concussion, I’ve had hundreds, probably thousands, throughout my career, which is frightening.”

Favre appeared on the show alongside former professional athletes Abby Wambach, David Ross and Kurt Warner, who are all investors in a company that is developing a concussion-treatment drug called Prevasol. The drug is currently in testing, and hasn’t been approved by the FDA yet.

Favre played 20 years in the NFL, and retired before Dr. Bennet Omalu made a breakthrough and discovered the existence of CTE — a brain disease caused by repeated head trauma. Since then, we’ve seen dozens of former NFL players (and boxers, hockey players, professional wrestlers, etc) pass away at a young age, and inevitably end up diagnosed with CTE (right now, it can only be detected via a posthumous autopsy).

“It has gotten a lot worse in regards to short-term (memory); simple words that would normally come out easy in a conversation, I will stammer,” Favre said. “And look, I am 48 years old … could it just be, as we all like to say, as we get a little bit older, I forgot my keys and they were in my hand. Or, ‘Where are my glasses?’ and they are on my head. I wonder if that is what it is, or do I have early stages of CTE — I don’t know.”

Favre also said that he supports changing the rules for youth football, including banning tackle football until kids are almost adults.

“The brain and just the skull itself, for (eight to 15-year-olds), and maybe even older, is not developed enough and they should not be playing tackle football,” Favre said. “We should protect them, especially when there is no treatment solution out there. Hopefully, Prevasol is that treatment.”

The NFL didn’t even have a concussion protocol for most of Favre’s career, only implementing it in the 18th of his 20 playing seasons. He played in an era where playing through injuries (even head injuries) was a sign of dedication or toughness. As the science of head injuries progresses, the entire game of football continues to adjust.

“The thought process then was you would never come out of a game or a practice because you had a little head ding,” he said. “It was a matter of being tough. Now what we know, it has nothing to do with toughness.”