Prokhorov was accused of a cover-up in an affidavit by Grigory Rodchenkov, who oversaw widespread doping as head of Russia’s doping control laboratory in Moscow.

“We categorically deny this story,” the Journal quoted a representative for Prokhorov as saying. “It is based on totally irresponsible hearsay and is complete nonsense.”

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According to Rodchenkov’s affidavit, he was told by Irina Rodionova, a Russian doctor who administered drugs to athletes, that Prokhorov paid “millions of rubles” to keep biathlete Irina Starykh from going public about her doping regimen in 2014 after she and fellow biathlete Ekaterina Iourieva were disqualified from the Sochi Winter Games for positive tests. Prokhorov was the president of Russia’s biathlon federation at the time.

Starykh, who did not go public, reportedly denied receiving any payments.

“Rodchenkov’s statement that I received some money from Prokhorov is a lie,” the Russian news agency TASS quoted her as saying Thursday. “I didn’t receive any money.”

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Prokhorov resigned from the biathlon federation after Russian athletes won just one gold medal in Sochi. Prokhorov guaranteed at least two gold medals.

A spokesman for the biathlon federation also tried to cast doubt on Rodchenkov’s claim.

“If it happened, no one knew about it,” Konstantin Boitsov told the Journal. “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.”

Rodchenkov’s testimony as a whistleblower was instrumental in the International Olympic Committee this week banning Russia from competing in February’s Winter Olympics in Pyeongchang, South Korea. Russian athletes who pass a series of doping tests can still compete, but under the Olympic flag.

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The NBA declined to comment on the Journal’s report.

Prokhorov owns 51 percent of the Nets after selling a 49 percent stake this year to Joseph Tsai, co-founder of the Chinese online company Alibaba. Tsai has an option to buy out Prokhorov in four years, the Journal noted.