The whistleblower at the heart of the International Olympic Committee’s case against Russia alleged in sworn testimony that Brooklyn Nets owner Mikhail Prokhorov paid a Russian biathlete millions of rubles not to disclose the elaborate doping scheme that has resulted in the country’s ban from the upcoming Pyeongchang Games.

The accusations suggesting the owner of an NBA team helped obscure the doping program in his role as the Russian Biathlon Union’s president are buried in a footnote deep in the affidavit of the saga’s central figure.

Grigory Rodchenkov, who oversaw the state-sponsored doping as the head of Moscow’s doping control laboratory, has explained the fraud in extensive detail since fleeing to the U.S., where he is now being held in protective custody. The IOC found him credible enough to levy the unprecedented punishment on Russia this week.

Unlike other claims in Rodchenkov’s testimony, many of which are supported by contemporaneous notes in his diary, the accusation that Prokhorov paid off a Russian athlete who tested positive for doping was repeated to Rodchenkov by an intermediary. There is no further evidence to support the accusation, and Prokhorov disputed Rodchenkov’s account on Thursday.

“We categorically deny this story,” a representative for Prokhorov said. “It is based on totally irresponsible hearsay and is complete nonsense.”

Russia's relay team from left, Yana Romanova, Olga Zaitseva, Ekaterina Shumilova and Olga Vilukhina, celebrate winning the silver for the women's biathlon 4x6k relay at the 2014 Winter Olympics. Photo: Kirsty Wigglesworth/Associated Press

When he bought the Nets in 2010, Prokhorov was already the president of Russia’s biathlon federation, an oligarch tasked with bringing Olympic glory to his country during the 2014 Sochi Games. Prokhorov had a mandate to spend lavishly and even promised to resign if Russia didn’t win at least two gold medals on its home turf. He acknowledged that his sport had been tainted by doping scandals, and international biathlon officials publicly credited Prokhorov in the run-up to the Olympics for his anti-doping crackdown.


But on the night of Jan. 28, 2014, less than two weeks before Sochi’s opening ceremony, Rodchenkov says he received an ominous call from Alexander Kravtsov, the head of Russia’s Olympic delegation. He informed Rodchenkov that biathletes Ekaterina Iourieva and Irina Starykh had been disqualified by the sport’s governing body after failing a doping test.

“This was a disaster so close to the Sochi Games,” Rodchenkov wrote in the affidavit.

The next day, Rodchenkov says he spoke with Irina Rodionova, the doctor who allegedly delivered the now-infamous steroid cocktail to Russian athletes and helped them replace contaminated samples with clean urine that would help them pass anti-doping tests.

Grigory Rodchenkov oversaw the state-sponsored doping as the head of Moscow’s doping control laboratory. Photo: sportphoto.ru/European Pressphoto Agency

She asked whether it was possible to “discredit the analysis,” Rodchenkov said. But since Iourieva and Starykh had been caught in Austria, he explained, there was nothing Rodchenkov could do to cast doubt on the results.


That’s when Prokhorov got involved, Rodchenkov said.

Rodchenkov says Rodionova later told him that Starykh was planning to reveal her doping regimen as orchestrated by Stanislav “Stasik” Dmietriev. Rodchenkov identifies him as a valuable source of Erythropoietin, otherwise known as EPO, providing Russian athletes with a form of the performance-enhancing drug that doping tests struggled to detect.

Starykh never went public with her first-hand knowledge of Russia’s doping scheme. Prokhorov paid the biathlete “millions of [rubles] to stay silent,” Rodchenkov said Rodionova told him.

“Rodchenkov’s statement that I received some money from Prokhorov is a lie,” Starykh said in a statement to the Russian news agency TASS. “I didn’t receive any money.”


Rodchenkov’s attorney said he believes Rodionova’s information was credible.

Prokhorov recently told local media the Russian national biathlon team underwent additional checks on the eve of the Sochi Olympics, and that the team was clean at the 2014 Games. Prokhorov himself criticized Rodchenkov when the IOC slapped lifetime bans last month on two other Russian biathletes who medaled in Sochi and said he would offer financial support if they took legal action.

Konstantin Boitsov, a spokesman for Russia’s biathlon federation, also disputed Rodchenkov’s accusation.

“If it happened, no one knew about it,” he said. “Mikhail Prokhorov was an important businessman who was more interested in the finances of the federation as well as his other projects, and didn’t have much contact with athletes outside of formal ceremonies.”


A spokesman for the NBA declined to comment on the allegations.

Team Russia during the Opening Ceremony of the Sochi 2014 Olympic Games. Photo: barbara walton/European Pressphoto Agency

Prokhorov sold a 49% stake in his team earlier this year to Alibaba co-founder Joseph Tsai, and included an option for Tsai to purchase the controlling share from Prokhorov in four years. Prokhorov stood to make hundreds of millions of dollars from the investment even though the Nets have been one of the league’s worst teams under his ownership. The sale valued the Nets at $2.3 billion less than a decade after Prokhorov bought his 80% stake and parts of the new downtown Brooklyn arena and surrounding real estate for $260 million.

Prokhorov made a defiant promise back then that might have sounded familiar to Russian biathlon fans. If the Nets didn’t win a championship in the next five years, he said, Prokhorov vowed to punish himself with the worst penalty he could imagine: marriage. The Nets haven’t won a championship. Prokhorov is still a bachelor.

But he kept his word on his biathlon pledge. Russia won one gold medal in Sochi, not two, and Prokhorov announced not long after the Olympics that he was stepping down as the biathlon president.

—Sara Germano and Thomas Grove contributed to this article.

Write to Ben Cohen at ben.cohen@wsj.com and Nathan Hodge at nathan.hodge@wsj.com