A Russia international, who participated at the 2018 FIFA World Cup, is reportedly being investigated by Spanish anti-doping authorities for an alleged violation.
According to BBC Sport, Denis Cheryshev, who is on loan at Valencia from Villarreal, is being monitored for the use of a growth hormone treatment (HGH).
The World Anti-Doping Agency has claimed that using HGH without a therapeutic exemption can lead to a four-year ban for the 27-year-old.
Cheryshev fell under suspicion after his father revealed his son had used HGH at some point, but later retracted the statement, saying his remarks, made before the latest World Cup, had been misquoted by a journalist.
Meanwhile, the forward, who scored four goals in five games at the global showpiece in Russia, believes he is completely innocent of any wrongdoing.
"On my side, everything has been honest and I think there will be no problem," Cheryshev said, according to BBC Sport.
"I think we'd better leave this case in the hands of medics, who have done everything right."
The on-loan Los Che star has made 18 appearances for his national team so far, scoring five goals along the way.
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