Mayweather said the beef began years ago when 50 Cent and Tommy Summers, a former associate of Mayweather, were trying to start their own promotion company.
The retired boxer told Simpson he grew upset when 50 Cent and Summers "[tried] to remove Al Haymon" from the picture. Haymon has been Mayweather's longtime manager. (warning: video contains profanity).
Mayweather also had less than flattering things to say about Power, the television series for which 50 Cent is a star and one of the executive producers.
"I watch Power," Mayweather said. "Even if he left the show, people still wanna watch the show. But as far as this season, it's s--t. It's been garbage... As far as the other seasons, it's been the best show."