Former UFC title challenger Chael Sonnen believes if Conor McGregor is to return to the boxing ring, he will only face Floyd Mayweather again.

Mayweather fought McGregor on 26 August in one of the biggest fights in combat sports history with both fighters earning nine figures.

While the Irishman lost to Mayweather via stoppage in the 10th round, he was praised for reaching that far against arguably the greatest boxer of all time.

Now expected to return the octagon, McGregor, however, has refused to shut the door on more boxing match-ups.

Most recently, retired boxer and promoter Oscar Del La Hoya, who notably promotes Canelo Alvarez, called him out for a fight.

"You know I'm competitive. I still have it in me," Del La Hoya told ESPN. "I've been secretly training, secretly training. I'm faster than ever and stronger than ever."

"I know I can take out Conor McGregor in two rounds. I'll come back for that fight. Two rounds. Just one more [fight]. I'm calling him out. Two rounds, that's all I need."

Sonnen did not expect a call-out from the Golden Boy Promotions founder but believes McGregor will only come back in the ring when the now retired Mayweather is in need of another money fight.

"That's [Del La Hoya call-out] a curve ball from left-field that nobody saw coming," Sonnen said on his official YouTube channel. "I don't think we're going to see Conor back in that ring until Mayweather goes through his money, which is going to happen."

"It will probably take a couple of years and we are likely to see a Conor-Mayweather 2 regardless of how many people are going to say 'Chael, you're wrong on that.'

"We'll need two to three years to see if I'm right but Mayweather will be back so if Conor's still hot at the time, Mayweather will still be hot. Comeback fights are huge. Mayweather will fight again, that part I'll tell you for sure."

As for Del La Hoya's call-out of the lightweight champion, Sonnen is intrigued as he knows the former champion is not in need of money. He also sees a potential match-up having legs.

"Del La Hoya all of a sudden calls him out. You don't see that one coming," he added. "We don't want to see Conor in there with Canelo, we get it. That's not what we want to see."

"Oscar damn sure doesn't need the money. Oscar Del La Hoya was rich, he made some good decisions. But even after he made a whole boatload of money, he went into promoting. He might be the biggest promoter in the world for boxing.

"All of a sudden, he wants to fight Conor. That has some major legs. An Oscar Del La Hoya comeback fight would be huge. That has my interest, just slightly. I'm not over the moon for it....I could see where that little spark could turn into a firestorm."