If Floyd Mayweather fights in the UFC, Demetrious Johnson says he knows exactly how it'd go down -- "He'd get his ass whooped." TMZ Sports spoke with the UFC's pound-for-pound king in Minneapolis ... and he laughed off the idea of Floyd competing in…
Former flyweight champion Mark Johnson believes Floyd Mayweather Jr. will have a hard time staying retired because the lure of the bright lights of boxing will be too much for the undefeated American. ?It's going to be very hard for Floyd to stay…