Chelsea winger Mykhailo Mudryk is appealing to the Court of Arbitration for Sport after he was given a four-year ban by the Football Association for doping.
CAS have confirmed they received his appeal against the FA on February 25. The FA, Chelsea and the player's lawyers have not commented.
Chelsea signed Mudryk for £88m from Shakhtar Donetsk in January 2023 and he still has five years left on his contract.
The positive test was for the prohibited substance meldonium which was administered abroad when Mudryk was not on Chelsea duty. Mudryk had played for Ukraine in Albania and Georgia in November 2024.
Mudryk was provisionally suspended by the FA in December 2024 after failing a drugs test.
In a statement the same month, Mudryk said his failed drug test was "a complete shock" and said he had "not done anything wrong".
Chelsea launched their own investigation shortly after the FA's began, and said the then 23-year-old insisted he "has never knowingly used any banned substances".
The Ukraine international, signed from Shakhtar Donetsk for £88.5m in January 2023, last played for Chelsea in a 2-0 win at German side Heidenheim in the Conference League on November 28, 2024.