According to former two division world champion Jessie Vargas, UFC superstar Conor McGregor was knocked out in recent sparring session.

McGregor is preparing to fight five division world champion Floyd Mayweather Jr. (49-0, 26 KOs), who at 40-years-old is coming back from a two-year retirement.

The fight is scheduled to take place on August 26th at the T-Mobile Arena in Las Vegas.

Speaking to Villainfy Media, Vargas claimed he had heard McGregor was knocked out while sparring in preparation for his August 26 fight against Mayweather.

“This guy got knocked out in sparring already,” Vargas said in a video interview.

The Las Vegas fighter did not reveal his sources or provide further details of the purported knock out -  “The boxing world is small so it’s a small circle.”

Vargas’ claim contrasts the accounts of McGregor’s sparring partners, who have been effusive in their praise of ‘The Notorious.’

“I don’t know if you’ve seen the photo that he uploaded onto his Instagram after our session,” amateur Irish boxer Tiernan Bradley told MMA Fighting earlier this month. “People are talking about his left hand and whether the power will be there with 10-ounce gloves — he lifted me off my feet with a right uppercut in 16 (ounce gloves)!

McGregor's head trainer, John Kavanagh, says his fighter was looked very solid in training.

"He will be very well-prepared. We have gone through one training cycle and we had in some good sparing partners, and, as we expected, his skills transcended over. He is not trying to win Wimbledon. It's not that different," Kavanagh said.

"His understanding of range, his understanding of how to move around is excellent. It's not completely different. There are some differences in this fight; he doesn't have to worry about someone shooting (kicking) on him. It's been a great experience. The first half has gone very well and I am heading out to Vegas for the second half on Monday, and I am expecting him to peak at the right time."