Sean O’Malley won’t be competing at UFC 229.

The popular UFC prospect announced Sunday on social media that he has failed a USADA drug test and will be unable to fight Saturday against Jose Quiñonez in Las Vegas. O’Malley wrote that he did not intentionally take a prohibited substance and has already identified a potential dietary supplement that caused the discrepancy.

“I have no intention and am fully confident that the results of this case will show that,” O’Malley wrote. “I love my fans and I hope the impact on my career is minimal and I’m back to fighting real soon.”

Previously, this would have been a situation announced by the UFC — that a fighter was facing an anti-doping policy violation. However, in July, the promotion changed its policy when it comes to announcing failed drug tests. They will only be made public once USADA’s investigation and adjudication process is complete and a sanction — or lack thereof — is decided.

This particular case is different, though. O’Malley is scheduled to fight in six days and he wrote he wanted to be open as to why he won’t be able to fight at UFC 229.

“Even though under the new policy, my case would not be public right now, I feel it’s important to be upfront and honest with my fans,” O’Malley wrote. … “We’ve sent remaining samples from the bottle I took to the USADA lab and [sic] as well as a full-sized bottle. I’m told the testing of these supplements can take as long as 30 days.”

It’s worth noting that O’Malley is a marijuana enthusiast, but cannabis metabolites are only prohibited in-competition, meaning this failed drug test would not have been due to marijuana. In-competition is only within the 24 hours before the fight until a few hours after it.

O’Malley (10-0) is one of the UFC’s most exciting prospects. The MMA Lab product is coming off a unanimous decision win over Andre Soukhamthath at UFC 222 in March. O’Malley, 23, was brought in after being on Dana White’s Tuesday Night Contender Series show and has won all three of his UFC bouts.