BOSTON (CBS) — The NFL may never again see a safety who hits as hard as Rodney Harrison.

That’s in part due to Harrison’s Hall-of-Fame-caliber level of play, but also to the changes to the rules that prevent many of the hits Harrison laid on receivers, running backs and quarterbacks from taking place on the football field anymore. Since Harrison’s final season in 2008, the league has made great strides in curbing head injuries, working to create a new era where the image of a defensive back “jacking up” a defenseless receiver is merely a thing of the past.

Harrison, though, didn’t play in that era, but he said on The Dan Patrick Show on Thursday that by so often being the hammer, he occasionally ended up being the nail.

“I think I had at least 20 or 30 concussions,” Harrison said on the show.

The number is certainly startling, especially considering it’s safe to assume most of them went unreported, as concussion awareness in the ’90s was hardly existent compared to the present day. Still, it’s not entirely surprising, and Harrison’s not even the only safety to admit to a high number of concussions on Patrick’s show this summer. Steelers safety Troy Polamalu told Patrick that he’s had “eight or nine” concussions and also that he’s lied about his health in order to stay in games.

Harrison, now a national football analyst, said on the show that he’s already starting to feel the effects of his head injuries, including memory loss and headaches.

“I’m scared to death of what may happen to me,” the 39-year-old said.