Former three-time light heavyweight world titleholder Sergey Kovalev has tested positive for synthetic testosterone, meaning his fight with up-and-comer Bektemir “Bek Bully” Melikuziev likely will be canceled.

The fight, contracted at a catch weight of 178 pounds, was scheduled to take place as the main event of a DAZN card at the Fantasy Springs Resort Casino in Indio, California, after having been moved this week from Luzhniki Arena in Moscow due to the worsening COVID-19 situation.

Kovalev gave a sample to the Voluntary Anti-Doping Association on Dec. 30 in Las Vegas, where he has been training, and the positive result was returned on Wednesday, according to the letter VADA sent to Kovalev’s team and others involved in the event outlining the details of the positive test.

“Adverse analytical finding: IRMS (isotope-ratio mass spectrometry) results are consistent with exogenous origin of testosterone and metabolites,” according to the letter, a copy of which was obtained by BoxingScene.com.

The letter, sent to the California State Athletic Commission, the Association of Boxing Commissions, Golden Boy Promotions and Main Events, added that “Mr. Kovalev has the right to promptly request analysis of the ‘B’ sample at his expense.”

“We are aware of the adverse finding from VADA,” Main Events CEO Kathy Duva, Kovalev’s longtime promoter, told BoxingScene. “Sergey Kovalev has been proven to be a clean fighter throughout the many years that he has been tested by VADA. VADA was contracted for this fight at his insistence, as he has requested for almost all of his fights going back several years. He maintains that he did not purposefully ingest any banned substances. We have made arrangements to have his supplements tested for contamination and will request that VADA test his B sample.”

Kovalev (34-4-1, 29 KOs), 37, a Russia native fighting out of Santa Monica, California, has not fought since he lost the WBO 175-pound world title to Canelo Alvarez by brutal 11th-round knockout on Nov. 2, 2019 at the MGM Grand in Las Vegas. Alvarez had moved up two weight classes to challenge him for his title.

Kovalev, who is owed a seven-figure comeback fight as part of the deal for the Alvarez fight, was scheduled to take on former light heavyweight world title challenger Sullivan Barrera at 180 pounds in the main event of a DAZN card on April 25 at Fantasy Springs, but that show was canceled due to the coronavirus pandemic.

Melikuziev (6-0, 5 KOs), 24, an Uzbekistan native fighting out of Indio, California, was an amateur standout and one of boxing’s top rising prospects.

Melikuziev, a southpaw, was willing to move up in weight to face Kovalev after having had his last bout at 168 pounds.

Dan Rafael was ESPN.com's senior boxing writer for fifteen years, and covered the sport for five years at USA Today. He was the 2013 BWAA Nat Fleischer Award winner for excellence in boxing journalism.