Sugar Ray Leonard -- Mayweather Ain't Retiring ... He Needs to Go For 50!!!

No one believes Floyd Mayweather is really retired from boxing ... nobody ... including boxing legend Sugar Ray Leonard who says he's convinced Floyd will get back in the ring to chase his 50th victory.

Of course, there's a huge buzz in the boxing world that Mayweather will "unretire" for a rematch with Manny Pacquiao ... who happened to announce Monday that his shoulder is all healed up.

Stay tuned on that one.

Side note ... Sugar Ray listed his top 3 greatest boxers of all time ... and Floyd didn't make the cut. Check out the clip.