Conor McGregor first set his sights on a showdown with Floyd Mayweather nearly three years ago, when he was just three fights into his UFC career, according to his head coach John Kavanagh.

It is expected to be one of the richest and most lucrative fights in combat sports history and it is a possibility McGregor has been contemplating since seeing Mayweather's name up in lights on the Las Vegas strip in September 2014.

But, his long-time head coach Kavanagh insists McGregor is being driven by the challenge of defeating the man who most consider to be the greatest boxer of his generation, rather than the huge riches on offer.

"Of course it is a nice payday. It would be silly to think that is not a huge factor in this fight," Kavanagh told Sky Sports News.

"But, above all, it is competition. He has obviously done quite well in the UFC. He kind of ran through the featherweight division and then he jumped up to lightweight and beat the champion Eddie Alvarez.

"So the competitive side of him was looking for what is the next big challenge. Then he and Floyd seem to be on this path that was going to cross eventually."

Kavanagh then opened up about McGregor's past and the fact that the Irishman was plotting a fight with the American a couple of years ago.

"It actually began a couple of years ago when Conor and I were out here for his fight with Dustin Poirier and Floyd was fighting the second Maidana fight while we were here. That caught his eye.

"Then, I guess the combat gods smiled on us and it led to this crossing of paths.

"I wonder what is going to go through their minds when Floyd comes back after round one, after round two, after round three and this half-crazy Irish guy is still laughing at him, talking to him, putting him under pressure and starting to land shots that they weren't expecting."

Many boxing experts have written off McGregor, who heads into the fight as a considerable underdog.

However, his odds have diminished drastically in recent weeks, proving that more and more people are beginning to back the Irishman.