Chelsea winger Mykhailo Mudryk has said he is shocked after being notified of a positive drugs test by the Football Association.

Reports in Ukraine on Tuesday suggest a prohibited substance was found in an “A” sample given at the end of October. Those same reports state the “B” sample has not yet been tested but will be in the coming days.

Confirmation that Mudryk has used a banned substance could trigger a lengthy ban from football, potentially up to four years.

A source told ESPN that Mudryk has been provisionally suspended pending the outcome of an investigation but the FA and Chelsea refused to confirm this when contacted by ESPN.

Mudryk, 23, has missed the club’s last five matches with head coach Enzo Maresca citing illness as the reason for his omission.

“I can confirm that I have been notified that a sample I provided to the FA contained a banned substance,” Mudryk wrote on Instagram.

“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.”

Chelsea said in a statement: “Chelsea Football Club can confirm the Football Association recently contacted our player Mykhailo Mudryk concerning an adverse finding in a routine urine test.

“Both the club and Mykhailo fully support The FA’s testing programme and all our players, including Mykhailo, are regularly tested. Mykhailo has confirmed categorically that he has never knowingly used any banned substances.

“Both Mykhailo and the club will now work with the relevant authorities to establish what has caused the adverse finding. The club will not be commenting any further.”

FA rules state that a player notified of a positive test result can be provisionally suspended by their club pending a right of reply and subsequent testing of a ‘B’ sample.

Mudryk joined Chelsea from Shakhtar Donetsk in January 2023 for a fee which could potentially rise to £88 million. However, his time in England has been mixed having started just 26 Premier League games and only one this season.

The Ukraine winger has been a regular in the Europa Conference League, where Maresca has made wholesale changes from his regular Premier League line-ups.