Calvin Johnson says it's no surprise to him that Roman Reigns has become one of the most legendary WWE Superstars of all time ... telling TMZ Sports the dude was a total "badass" at Georgia Tech.
Believe it or not, the guys were actually teammates for the Yellow Jackets' football team in the mid-2000s ... and Johnson says he knew right away that Reigns had mega-star potential.
"He was just always like a badass," the Hall of Fame wide receiver explained. "He didn't say much, but when he did say something, you listened.