Khalil Rountree says he's out of UFC 303 co-main after taking banned substance

Khalil Rountree will no longer be fighting former light heavyweight champion Jamahal Hill for UFC 303's co-main event, according to Rountree himself on Saturday.

The 34-year-old says he inadvertently took DHEA, a substance prohibited by the UFC's anti-doping policy, and upon realizing what happened he took it upon himself to report the occurrence to Jeff Novitzky, UFC senior vice president of anti-doping compliance, and Donna Marshall, UFC vice president of anti-doping compliance.

In a social media post Rountree said he's "gutted to deliver this news to you all, but I will not be fighting at UFC 303 due to consuming a banned substance."

"I did not do this intentionally and I am doing everything I can to get this situation taken care of," he added.

The Los Angeles native says he consumed the banned substance in a blend mistakenly provided by a personalized supplement service that had worked with him in the past.

"I've provided (the UFC) with all of the information to show that this was not a matter of cheating or to enhance performance," Rountree wrote. "My sincerest apologies to you all and to Jamahal for this unfortunate series of events."

To say it's unfortunate timing for Rountree, who was just over a month away from one of the biggest fights of his career, is an understatement. He was entering the co-main bout on the heels of a five-fight win streak, his last victory coming by way of a knockout of Anthony Smith that vaulted him into the top 15.

Many believed the new No. 8 contender in the light heavyweight division was well on his way to a title shot if he had beaten Hill in June.

UFC has yet to make any formal statements on the matter. UFC 303 is expected to be one of the biggest events ever for the promotion, as it'll be headlined by Conor McGregor in his much-anticipated return, taking on Michael Chandler from T-Mobile Arena in Las Vegas on June 29.