UFC 219's Holly Holm has given advice to Floyd Mayweather regarding the sheer difference between boxing and UFC - calling it 'a whole different world in MMA'.

This comes after Mayweather claimed he would make millions of dollars fighting in the Octagon, but after reported talks with UFC president Dana White, 'Money' revealed, whilst he could fight McGregor in UFC, he has no desire for a rematch.

Irishman McGregor called Mayweather a 'p***y' on Instagram earlier this week in the hope of provoking a reaction.

Holm will encounter Cris Cyborg UFC 219's main fight for the women's featherweight title on December 30.

She has been one of the few combatants to have progressed well in boxing and MMA.

Holm holds a record of 38 fights with 33 wins, three draws, and two defeats in boxing, while in UFC, it's 11 wins and three defeats. 

The 36-year-old former bantamweight and heavyweight champion was also an amateur kick-boxer before she began her MMA and boxing stints.

Albuquerque-born Holm offered her thoughts on how the transition would be if Mayweather attempted to try UFC.

"It is a whole different world in MMA," Holm told TMZ. "I think one of the biggest things that I tell people was the hardest going from boxing to MMA is, kind of that inside boxing.

"You'd get comfortable sitting in the pocket wanting to throw punches, and you'd have this other person coming at you and just clinches onto you. In boxing you clinch a bit and the ref breaks you up, but in MMA (if) they clinch you, they take you down.

"So it doesn't mean that he can't learn it. But it's going to be a whole different gameplan from what he's doing in his boxing career. But I don't put it past anybody to be able to do the transition," she added.

Dana White's supposed talks with Mayweather, and McGregor's social media conduct, means that we should by no means rule out a UFC fight between the pair.

But, like the latter's move to boxing, Mayweather should be cautious as to the challenges he may face if he is to enter the octagon.