McGregor will be competing in his first sanctioned boxing match against a boxer widely regarded as the best of his era, and arguably the sport's greatest-ever defensive fighter. "It's just ridiculous to me", Lewis went on to say.
Still, at least there's one person in the world who thinks this fantasy fight isn't a foregone conclusion.
It is unclear how many bouts will proceed the main event with many suggesting Mayweather vs McGregor would not need any introduction.
There are two key factors that determine the total gross revenue of a fight (how much money it makes in simple terms), and then a number of other parties who clip the tickets.
"Conor McGregor is a two division world champion at mixed martial arts, Conor would get him out of there very quickly and there would be no talk amongst MMA guys that it was going to go the distance, it would just be an open and shut case", said Sonnen.
According to Metro, both the Irishman and Mayweather look set to make over $100million or £80m each on fight night.
In the United States of America alone, the Mayweather vs Pacquiao fight is reported to have landed between 4.0 and 4.8 million buys, meaning a gross revenue of around $450 million U.S., over $500 million AUD.
Golovkin (37-0, 33 KOs), 35, insists his fight with Alvarez (49-1-1, 34 KOs) is bigger and of more significance than Mayweather-McGregor, which he sees as a "circus show".
Floyd himself thinks differently, saying that he raked in $25 million before he stepped into the ring, and made $300 million on the Pacquiao bout.
Broner called out Diaz while at a press conference promoting his July 29 fight against the undefeated Mikey Garcia: "After this fight, if I come out untouched, I feel like I should come back and fight on Floyd's undercard against Nate Diaz", Broner said to the giggles of those in attendance. But, even McGregor's team has to understand why the vast majority of people who understand fighting, believe that Mayweather is going to win, and do so, pretty easily.
Mayweather fights McGregor three weeks earlier in the same city, Las Vegas.
Mayweather-McGregor is expected to do astronomical numbers for revenue and television viewers, but its competitive value is questionable.
"If they got in close and Floyd was shucking and juking on the outside and he threw a jab to cover up a left high kick and that left high kick necks him? I love Bruce Lee and the other disciplines and when he fought against other fighters, you wanted to see the differences, so I can see the appeal", Lewis said.