Chelsea head coach Enzo Maresca said he believes Mykhailo Mudryk did not knowingly take a banned supplement.
The 23-year-old has missed the last five matches having returned a positive drugs test with the club confirming on Tuesday the reason for his absence, having previously claimed that he had been missing through illness.
Mudryk said in an Instagram post that the results of his 'A' sample had come as a "complete shock" and insisted that he not intentionally taken a banned substance, reported in Ukrainian media to be meldonium.
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"We trust Misha," said Maresca. "When this kind of thing happens you need to support your player in all aspects.
"Misha is a Chelsea player, it's my duty to be in contact with him. Me, the club, his teammates, we are all there.
"Trust means we believe Misha."
The PA news agency understands the 23-year-old has been provisionally suspended as a result of the failed test.
The Ukraine international has struggled for consistency since joining from Shakhtar Donetsk in January 2023 for £88million, making 53 Premier League appearances but scoring only five goals.
This season he has mainly been used in the Carabao Cup and in the Conference League for Maresca who has used him only sparingly as a substitute in the league.
The head coach said he expects Mudryk to still have a future at Stamford Bridge following any long-term suspension that may be handed down.
"I think he's going to come back, the only thing is we don't know when," said Maresca. "The only doubt we have in thus moment but for sure he's going to come back.
"Any player in the world when this happens, they need support. No matter if he's 20 or 30, no matter if he's English or Italian or Ukrainian. When this kind of things happens, we all need support. It's not about his age or his country.
"It is my duty since we started. I try to have a quite close relation with the players, because I like it that way.
"With Misha it is exactly the same. I'm there to try to help him in anything he needs because in this moment it's normal that he's going need help from the club, from me, from his teammates, and we are all there to try to support."
