Floyd Mayweather's age could catch up with him against a "hungry" Conor McGregor, according to Jonny Nelson.
Five-weight undefeated champion Mayweather, 40, will put his perfect 49-0 record on the line against McGregor - who has never boxed professionally before - at the T-Mobile Arena in Las Vegas on August 26.
McGregor's mixed martial arts background should not be underestimated though, according to former world cruiser-weight champion Nelson, with the age gap between the pair potentially having a surprise impact.
"The one thing you have to look out for, let's not forget, Floyd Mayweather is 40 years old," Nelson told Sky Sports News. "He's been out of the ring for a while.
"I know he's top tier, we're thinking there's no chance this guy [will lose], but Conor McGregor is very fast individual, he's got power in both hands.
"We want to see how age has affected Floyd Mayweather. In my head, Floyd does it hands down, but let's not forget he's in there against a 29-year-old hungry man that can hit, that's fast and that wants it. So it is not a done deal."
McGregor's lack of technical experience will put the Irishman up against it when he gets in the ring with Mayweather though, according to Nelson, with past examples proving those entering boxing from MMA need time to adapt.
"Guys that come from mixed martial arts, if you're top level, you will blitz everybody until you come against someone who is technically supreme at boxing because your defence is too open," Nelson added.
"You saw this with Wladimir and Vitaly Klitschko. When they first came into boxing, especially Wladimir, he was getting knocked out, pick-pocketed, especially when he came against class fighters.
"They've got to tighten up a bit, change the balance, change the positioning. But fitness is second to none."
Although the odds may be stacked against McGregor when the fighters meet in the ring, there is no doubt who has the upper hand following the transatlantic tour to hype the fight, according to Sky Sports boxing commentator Adam Smith.
"He [McGregor] was absolutely sensational, the way he manipulated Floyd in London," said Smith. "He definitely won the press conference tour.
"Never seen anything like it in boxing. It was immense. It was a phenomenal atmosphere. I think I've fallen in love with Conor McGregor over the past week, he is such a personality, he oozes charisma."
Nelson added: "Floyd is there trying to psyche him out, it is not going to work at this stage. This is what McGregor is used to."