Coach John Kavanagh says Conor McGregor is motivated by competition, not money.

Although Conor McGregor is marketed as a charismatic Irishman with an unhealthy obsession with money and three piece suits, 'The Notorious' is also a dedicated student of combat sports and, mixed martial arts, in particular.

In the lead-up to arguably the biggest fight in combat sports history, Conor McGregor vs. Floyd Mayweather Jr., much of the focus has been on one thing: money.

McGregor's full paycheck hasn't been disclosed, but it's expected that the 28-year-old megastar will make $100 million on August 26. Given that he'll be making infinitely more money than he would in the UFC, fans have predicted that the lightweight champion will retire after his boxing showdown with Mayweather.

But, according to SBG Ireland head coach John Kavanagh, who has been training with McGregor since he was a youngster, the UFC lightweight and former featherweight champ is motivated by the challenge and thrill of competition.

Kavanagh expects McGregor to return to the UFC by December.

“I don’t see any reason why he would not,” Kavanagh said of McGregor returning to the UFC on Monday's edition of The MMA Hour. “Certainly money would not be the reason why he would not do MMA again. He has said very clearly to me, ‘Get ready, we’re back in the cage in December.’ I hope someone out there has sparked the interest in him to make him excited about that.”

"It’s not money that’s motivating him anymore,” Kavanagh continued. “He could very easily make similar money from doing some movies or doing endorsements. It’s the challenge. That’s why he’s in the gym laughing every day. If he left the gym now and stopped fighting, what would he do with his free time? You can only sit in one car at a time, you can only have one meal at a time. Eventually you want to do something that’s enjoyable to you. And that would be Conor drifting back into the gym. It’s what’s enjoyable to him.”

According to UFC president Dana White, top-ranked lightweight contender Khabib Nurmagomedov has sparked McGregor's interest for a fight in Russia.

“He said, ‘I want Khabib in Russia,'” White said of McGregor in an interview with MMAjunkie. “Isn’t he (expletive) awesome? He’s like, ‘I want Khabib, in Russia.’ He’s awesome. Conor McGregor is a (expletive) unicorn. There’s nothing like him. He’s working on boxing Floyd Mayweather and then he’s talking about fighting Khabib in Russia right after.”

Kavanagh, a specialist in Brazilian Jiu Jitsu, says McGregor is most motivated when he's told he can't achieve something. That's the reason he accepted the fight with Mayweather, and that could also be the reason he wants to return against Nurmagomedov.

“The motivation for this fight was not money, though of course it’s nice to be well paid for what you do,” Kavanagh said. “It was the challenge. And to be told again it’s impossible to do what he’s saying clearly what he is about to do.”

Mayweather vs. McGregor is expected to take place on August 26 at the T-Mobile Arena in Las Vegas, Nevada.