The 25-year-old Ukraine international has not played since November 2024 following an adverse finding in a routine urine test which led to a provisional suspension in December of that year.
He was formally charged in June 2025 and subsequently handed the maximum four-year ban by the FA.
The FA has never publicly disclosed the substance involved, though the BBC understands that Mudryk came into contact with the cardiovascular medication meldonium — which can increase respiratory capacity and stamina — while on international duty with Ukraine in October 2024.
The Court of Arbitration for Sport confirmed the appeal in a statement to BBC Sport: "Cas confirms it has received an appeal by Mykhailo Mudryk against the FA, filed on 25 February 2026. The parties are currently exchanging written submissions, and a hearing is yet to be scheduled."
Bans in such cases are typically backdated to the start of the provisional suspension, which would place his current return date at around December 2028. A successful appeal could significantly reduce that timeline.
Mudryk, who joined Chelsea for an initial €70 million in January 2023, is being represented by Morgan Sports Law — the firm that also represented Paul Pogba during his doping case at Juventus, Tyson Fury and cyclist Chris Froome. He is currently maintaining his fitness by training at non-league Uxbridge FC with a private coach.
In his only public statement, issued when the provisional suspension began, Mudryk said he was in "complete shock" and had "never knowingly used any banned substances or broken any rules."