Yeray Alvarez has been given a 10-month ban following a positive doping test after playing Manchester United last season.
Alvarez started both games against Manchester United as they lost 7-1 on aggregate in the Europa League.
The 30-year-old tested positive for a banned substance found in a medicine used to prevent hair loss following his cancer treatment.
Yeray Alvarez given 10-month suspension after banned substance mistake
Alvarez was found to have tested positive for canrenone, which is a diuretic that can sometimes be used as a masking agent.
He was diagnosed with testicular cancer in 2016 and had been taking the medicine to treat hair loss ever since.
Alvarez's defence admitted he had mistakenly ingested the substance by taking a medicine to prevent alopecia.
Although UEFA acknowledged and accepted Alvarez explanation that he did not mean to take the banned substance, they still found him guilty of committing a "non-intentional anti-doping rule violation."
He accepted a provisional suspension in June so his ban will be backdated. He will be able to play again from April 2, 2026, and will be allowed to train from February 2, 2026.
He has won the Copa del Rey and Supercopa de Espana during his time with Athletic Club.
Athletic Club are back in action Alaves before kicking off their Champions League campaign at home against Arsenal.
Alvarez has made 257 appearances for the Basque club, despite the battle with illness earlier in his career.
