Oleksandr Usyk’s heavyweight debut is this weekend, but he will apparently need a new opponent.

The former undisputed cruiserweight champion was scheduled to face former kickboxing star Tyrone Spong (14-0, 13 KOs) this Saturday in Chicago on DAZN, but it looks like that’s off the table.

Eddie Hearn, Usyk’s promoter, confirmed that there was an “adverse finding” in one of Spong’s VADA conducted drug tests.

We have been contacted by VADA to inform us that there has been an adverse finding in Tyrone Spong’s test,” Hearn tweeted. “It has been sent to the State of Illinois commission and further information will be released in the morning. We have reserve opponents standing by.

Usyk (16-0, 12 KOs) was slated to fight Carlos Takam in May, but withdrew due to a biceps injury. Takam then signed with a promoter and wanted a bigger payday, which nixed the rescheduling of the matchup. Finding an opponent proved difficult for this October 12th date, and Spong was not even Option A or B.

It is not known what banned substance Spong tested positive for, but Mike Coppinger of The Athletic says that he won’t be fighting Usyk anymore. We’ll presumably know a replacement opponent shortly, but don’t expect anyone particularly good.

Update: ESPN reports that Spong failed for clomiphene, which is the same substance that Brock Lesnar and Jon Jones failed separately for at UFC 200.