Earlier this week, Floyd Mayweather claimed that he could make a billion dollars in a three- or four-fight deal with the UFC if he returned from retirement.

He said, according to ESPN: "They just called me not too long ago and ask me to come back. I can come right back. If I wanted to I could come right back to the UFC. I can go fight in the octagon. I can go do a three- or four-fight deal in the octagon and make a billion dollars. Remember I'm Floyd 'Money' Mayweather."

It's only been five months since Mayweather's famous fight against UFC Lightweight Champion Conor McGregor, yet the former boxing champion is already thinking of coming out of retirement once more for another payday, and it seems like he might already have a challenger for his first UFC fight.

While the obvious opponent for Money, if he was to join UFC, would be another clash against The Notorious, except this time inside an Octagon and not a ring, another UFC Champion has thrown his hat in the ring as a possible opponent for the undefeated boxer.

Speaking at the UFC 221 preview event in Sydney, Robert Whittaker said that he would "100 percent" fight the boxing legend in the Octagon if the opportunity presented itself.

The UFC Middleweight Champion said: "I think even my dad would fight him for the pay grade. It would be an honour, but I don't even think it's a feasible idea. He's much smaller than I am, and I'm not a bully."

In fact, Whittaker is open to any boxer making the transition to the Octagon, but he warns them that it's not going to be as easy for them as they may think.

"They can do what they want, it doesn't bother me. If Mayweather wants to come over and fight in the UFC then do it. It's hardcore here, though. I don't think it'll be a stroll in the park. Granted he's the best boxer ever seen, just about.

"I don't mind, I think it's great for both sports. It brings the spotlight on both sports and I think crossing them over is fine, but for the safety of the athletes I think everyone needs to be properly prepared. Especially guys moving into MMA because of the diversity of the skillsets."

Until Mayweather signs the dotted line to join UFC, Whittaker will have to settle for the time being to defending his Middleweight title against Luke Rockhold at UFC 221 in February 2018.