Middlesbrough defender Abel Xavier has vowed to fight his 18-month drugs ban in court after testing positive for an anabolic steroid.The Portuguese full-back, 33, is expected to go to the Court of Arbitration for Sport to contest UEFA's guilty verdict. Xavier became the first Premiership player to be found guilty of taking performance-enhancing drugs when a routine test last September showed the presence of methandienone, also known as dianabol, a steroid mainly used by body-builders. He insists it was the result of medication he was taken for a virus which affected his immune system. According to Mozambique-born Xavier the virus was caused 'maybe because of the weather in England, maybe because I'm African'. The positive test was taken following Boro's UEFA Cup match against Greek side Xanthi on September 29 and he was given the suspension at a personal hearing at UEFA headquarters in Nyon in November. An initial appeal to UEFA failed in December, leaving Xavier facing a bleak future and potentially the sack from Middlesbrough, who he joined in August 2005 after being released by Italian side Roma. Boro are giving Xavier the opportunity to clear his name, and he told Sky Sports News: 'I will appeal. At this moment I have the right to go to a civil court because I just want a fair and common sense decision. 'I will fight. I will go to the end, like I've done before, because at this moment I cannot work and I think it was very, very severe, an 18-month ban.' Xavier has been capped 20 times by Portugal and has played for both Liverpool and Everton as well as Benfica, Galatasaray and PSV Eindhoven. He is being given little chance of succeeding in an appeal, however, with Professional Footballers' Association chief executive Gordon Taylor downbeat about his prospects. 'It's difficult now to try to take a civil action,' said Taylor, 'because we feel the judges are going to say `the rules were clearly laid down, and although you do clearly protest your innocence and you're a very credible and intelligent person, the rules say that if you're on any medication for a virus there was ample opportunity to tell the Middlesbrough club doctor'. 'They could tell UEFA and the drug testers it's a therapy waiver and it's laid down clearly, so that when the sample he was taking was contaminated and containing an anabolic steroid then that would have been a legitimate excuse. 'Abel continues to protest his innocence and he has a right of course to go the civil court, but I think it's going to be an extremely difficult case to turn around now.'