Oleksandr Usyk’s first heavyweight fight against Tyrone Spong on Saturday is in doubt after promoter Eddie Hearn revealed the Ukrainian’s opponent has returned an adverse doping test.

Unbeaten Usyk is due to begin his pursuit of dominance in another division this weekend, live on Sky Sports, after becoming undisputed cruiserweight champion.

Tyrone Spong has returned an adverse doping test ahead of his fight with Usyk Tyrone Spong has returned an adverse doping test ahead of his fight with Usyk Tyrone Spong has returned an adverse doping test ahead of his fight with Usyk

But his opponent for his first heavyweight bout in Chicago is in jeopardy after testing by the Voluntary Anti-Doping Association (VADA).

Hearn tweeted: “We have been contacted by VADA to inform us that there has been an adverse finding in Tyrone Spong’s test.

“It has been sent to the State of Illinois commission and further information will be released in the morning.

We have been contacted by VADA to inform us that there has been an adverse finding in Tyrone Spong’s test. 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.

— Eddie Hearn (@EddieHearn) October 7, 2019

“We have reserve opponents standing by.”

Usyk’s heavyweight debut is long-awaited after he was forced to withdraw from his first fight earlier this year against Carlos Takam with a bicep injury he sustained in training.