It's 4 actually. Nagurski, Butkus, Lombardi, and now Bednarik.
He's just having one of the best seasons a LB has ever had, statistically. Far better than Manti Teo's Heisman runner up season, for the sake of comparison. He's responsible for 11 turnovers by himself, most teams don't break 20 total on the season. He's been the highest graded player (not just defensive player) in college football for the entire season per PFF.
He's also one of the few players I saw last season take on Skattebo head on and win. He's just one of those dudes, knows exactly what he needs to do in every situation, just flies around and makes plays, great leader, etc etc. Every team has had one from time to time, he'll be sorely missed after this season. Just one of those completely irreplaceable players, no matter how good/talented the next guy up is.
e: It's why it's just objectively a complete joke that he wasn't invited to the Heisman ceremony at least. They didn't have to trim it to 4, they invited 5 players last season. Every Tech fan knew he was never going to win it no matter how much they padded his stats with offensive touchdowns and shit, but he 1000% deserved to be there.