Mykhailo Mudryk is facing a potential ban of up to four years after the Football Association charged the Chelsea winger with a doping offence.
The 24-year-old was provisionally suspended in December having tested positive for a performance-enhancing substance named meldonium.
The Blues were awaiting the results of a 'B' sample test to support or contradict the initial 'A' results and the FA announced on Wednesday that the Ukrainian winger now faces potential further punishment.
"We can confirm that Mykhailo Mudryk has been charged with Anti-Doping Rule Violations alleging the presence and/or use of a prohibited substance, in terms of Regulations 3 and 4 of The FA's Anti-Doping Regulations," said the FA in a statement. "As this is an ongoing case, we are not in a position to comment further at this time."
Chelsea declined to comment on the FA's latest action. Guidelines suggest Mudryk could now face a lengthy suspension despite the player previously denying knowingly breaking any rules.
Sources have told ESPN that the drug was likely administered while he was outside of the United Kingdom.
Shortly after his initial suspension became public knowledge in December, Mudryk wrote on Instagram that "this has come as a complete shock as I have never knowingly used any banned substances or broken any rules, and am working closely with my team to investigate how this could have happened.
"I know that I have not done anything wrong and remain hopeful that I will be back on the pitch soon. I cannot say any more now due to the confidentiality of the process, but I will as soon as I can."
