Shawne Merriman has an insider's perspective when it comes to what makes NFL players and MMA fighters tick – and the parallels astonish him.

"There are a lot of similarities," Merriman recently told MMA Junkie Radio. "It's kind of scary when you think about it. It's obviously two different types of disciplines and two different types of work. The attitude and the mindset when you get around these fighters and these football players are very, very similar. First of all, you have to be crazy as hell to do both. The second part of that is just the discipline and how far some of these guys and women are willing to go. So the mindset is very, very similar."

A former NFL star, Merriman now runs his own MMA promotion, Lights Out Xtreme Fighting (LXF), based out of California. While he might be a bit biased, as a former linebacker for the San Diego Chargers and Buffalo Bills, Merriman said without question where the toughest of the toughest lie on the football field.

"Outside linebackers and defensive ends, it's always been that way," Merriman said. "The offensive lineman are big. But believe it or not, most of those guys are smiling and laughing. They're just big, jolly guys. The interior guys, the d-lineman, are a little bit meaner. But man, you get to some of these outside linebackers and defensive ends, that's when you start coming across the scariness. Some of these guys are pretty crazy."

While significant-name football-to-MMA crossovers have been limited to the likes of Herschel Walker and Greg Hardy (though there are the Brock Lesnars, Brendan Schaubs, and Matt Mitriones of the world), Merriman thought for a bit about which past or present NFLer that would've succeeded the most inside the cage. Then it hit him.

"It's funny. Eric (Nicksick), over at Xtreme Couture, has trained Patrick Willis and held mitts and things like that, and has told me he can go," Merriman said. "I think that if Patrick decided, and I was just with him at the Hall of Fame induction for Antonio Gates, I actually talked to him about this, I think he'd have been a hell of an MMA fighter if he turned right when he retired."

Merriman's promotion returns Saturday with LXF 28 at Thunder Studios in Long Beach, Calif. The card is headlined by a title fight battle between Bellator alumni Renato Valente (11-8) and Grant Neal (11-2).

This article originally appeared on MMA Junkie: Former NFL star compares UFC toughness to football players

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