Middlesbrough defender Abel Xavier was banned by UEFA for 18 months on Wednesday for failing a drugs test.
The 32-year-old Portugal international tested positive for the banned anabolic steroid dianabol after a UEFA Cup tie against Greek club Xanthi on September 29. The analysis of a B-sample confirmed the initial finding.
"The player was found guilty of being in breach of UEFA anti-doping regulations," UEFA said. "As a result, the UEFA Control and Disciplinary Body decided to impose an 18-month ban on Abel Xavier."
Xavier, who has three days in which to appeal, has denied any wrongdoing. Last month he issued a statement saying he was "convinced that there is a reasonable and entirely harmless explanation for such a positive finding, should it be confirmed by the analysis of the 'B' sample."
It is the second time Xavier has served a lengthy ban imposed by UEFA. The defender was suspended for nine months after Euro 2000 following a controversial end to Portugal's semi-final against France.
Portugal lost to a late "golden goal" penalty after Xavier was judged to have handled near the goal-line. Xavier, incensed by the decision, grabbed the arm of the assistant referee. His ban was later reduced by three months on appeal.
Xavier joined Middlesbrough at the end of August on transfer deadline day after a spell in Serie A with AS Roma.
He has played previously for Bari, German club Hanover 96 and for Everton and Liverpool in England. He also had a loan spell with Galatasaray in Turkey.
Born in Mozambique, Xavier has played 20 times for Portugal and hoped joining Middlesbrough would help him earn a recall in time for the 2006 World Cup finals.
Middlesbrough manager Steve McClaren told the club's website: "I've just been told and I'm very disappointed.
"Obviously, we know the implications of the ban. We've got to digest everything which has happened and we'll be making a statement on Friday or Saturday."