Francis Ngannou has been told to avoid a boxing showdown with Tyson Fury as the pair continue to talk up a crossover bout.
The Cameroon star retained his UFC heavyweight title against Cyril Gane at UFC 270 in what could be his final fight under the promotion.
He is expected to open talks over a new deal but is unlikely to accept the terms unless he is allowed to pursue a boxing meeting with Fury alongside his MMA career.
But UFC heavyweight Tom Aspinall believes Ngannou will realise that he needs some "serious work" ahead of any potential bout with Fury which has been talked up by the pair.
"Don't do it. Don't do it, man," Aspinall told The Mac Life. "I think people like MMA fighters that think they can box, they can box well for MMA!
"But when you're fighting actual boxers, they need to seriously do something like hard sparring with world-level boxers. And then, they will be like, 'Oh s**t, actually I need some serious work here.' It's like American football and rugby.
"They're both contact sports, they both involve a ball where you're running at each other, but they're completely different. There's a lot of aspects that are the same but they're boxers, mate. They can really punch."
Ngannou's pursuit of Fury began previously when he hinted at a boxing move after being unhappy with his earnings as his row over fighter pay continues.
Fury earned an estimated £20million for his trilogy clash with Wilder last year which is understood to have been fifty times more than Ngannou's earnings for his clash with Gane.
The UFC's undisputed champion wants to take on boxing's leading stars and believes his power can help him knock out the likes of Fury and Wilder.
The 'Gypsy King' challenged Ngannou to a mixed rules bout which the UFC star gladly accepted before proposing a rule set of his own.
He spoke of his desire to face Fury next in the fight week build-up to his recent defence, stating that he would like to face Fury next over any further title defence against Jon Jones.
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However he admitted he will be unable to pursue any shot at Fury until his future is resolved with Dana White telling Ngannou he is free to leave.
Ngannou posted another fight poster for the clash on social media in the aftermath of his victory.
Meanwhile Fury immediately responded to his latest win congratulating him before reiterating his call-out.
A fight looks unlikely in the near future with Ngannou also now requiring knee surgery which could leave him sidelined for nine months.
However he remains keen to test his ability in the boxing ring in the future, and believes the "sky is the limit" after his success in the octagon.
"I really want to be a boxer," Ngannou said in a recent YouTube video. "It's not a one time thing that I want.
"The sky is the limit, it won't be easy at all, when you see the belt holder like Tyson Fury you know they're not going to be easy, they are legit."
