Leonard, known as one of the 'Four Kings' alongside Marvin Hagler, Thomas Hearns, and Roberto Duran, didn't hold back when asked about his place in boxing history compared to Mayweather's.
"Absolutely [I was greater than Floyd], and I'm not bragging but then again my mindset as a fighter, as a champion will always tell me I could beat Mayweather, I could beat Tyson, that's what made me who I became."
Leonard's career speaks for itself. He won world titles in five weight classes and held the undisputed welterweight championship in 1981. His confidence also stems from a personal connection to the Mayweather family. In 1978, Leonard knocked out Floyd Mayweather Sr., a fact he's quick to remind Floyd Jr. about.
"I knocked your father out. Like father, like son."
Despite his bold claim, Leonard didn't discount Mayweather's skills. He acknowledged the difficulty in fighting the Michigan native, who retired with an unblemished 50-0 record.
"There's no one way to fight Floyd Mayweather, he is that good, he is that talented. No one could penetrate his defence, he was one of the best guys out there."
Mayweather's career certainly stacks up well against anyone's. The 48-year-old won 15 world championships across five weight divisions. He beat a who's who of boxing greats including Oscar De La Hoya, Manny Pacquiao, and Canelo Alvarez. His final fight saw him stop UFC star Conor McGregor in 2017.
Leonard's own resume is equally impressive. As part of the 'Four Kings', he was involved in some of boxing's most memorable fights. His world titles across five weight classes and undisputed welterweight reign in 1981 cement his place among the greats.
The debate over who ranks higher will likely continue among boxing fans. Both fighters brought unique skills and achievements to the ring. Leonard's confidence in his abilities, even in retirement, shows the mindset that made him a champion. Whether you agree with his assessment or not, there's no denying the impact both men had on the sport of boxing.
You can watch Leonard's full comments in this short video clip.