Xavier promises to prove his innocence

The Middlesbrough defender Abel Xavier has denied he deliberately took a performance-enhancing substance and will undergo a series of medical tests in an attempt to clear his name of drug allegations.

The 32-year-old is facing the prospect of a two-year ban from football, and the possible sack from Middlesbrough, after producing a positive urine sample in a random drug test taken following the Uefa Cup first-round tie against Skoda Xanthi on 29 September. The former Portugal international could have his one-year contract terminated by the Teesside club and an eventful career that has included four different clubs in the last three years will end in disgrace if his 'B' test also proves positive.

However, the much-travelled defender, who once claimed that his bleached blond hairstyle was a symbol of protest at his dismissal for handball in the Euro 2000 semi-final against France, vowed to prove his innocence in an impassioned defence last night. A statement from Xavier read: "Middle-sbrough yesterday evening informed the press that in the anti-doping control I had to undergo after the Uefa Cup match, I tested positive. I hereby confirm this fact. In the course of next week, the 'B' sample will be analysed. I am convinced that there is a reasonable and entirely harmless explanation for such positive finding, should it be confirmed by the analysis of the 'B' sample. In order to furnish this proof, I currently undergo [sic] a number of tests in which certain of my body fluids and tissues are analysed."

It continued: "Given the fact that the anti-doping regulations establish a purely objective responsibility (the athlete is guilty as of the moment when the most minor trace of a prohibited substance is found in his body), I currently have to furnish scientific and factual proof to establish that if a prohibited substance is found in my body, this is by no means because I would have had the intention to 'dope' myself."

The illegal substance discovered in Xavier's first test has not been specified but is believed to have come from a supplement he had imported from the United States to combat a virus. However, Middlesbrough, though currently standing by their £25,000-a-week player, were unaware that he was taking any additional supplements and will move to sever ties with the full-back if he is handed a lengthy suspension.

Xavier's 'B' sample results will be released next week and the chief executive of the Professional Footballers' Association, Gordon Taylor, admits the failure to inform Middlesbrough of the supplements has not helped his protestations of innocence. He has also warned the defender that although football does not apply the same disciplinary procedures as athletics - which would result in an automatic two year-ban for such a charge - Fifa's determination to show it has adopted a tougher stance on drug misuse could lead to an enforced absence from the game.

"Normally the 'B' sample is consistent with the first," said Taylor. "And it's a worry because we've gone high profile with circulars to players, and to club doctors and physiotherapists, that if you're taking anything you have to OK it with the club because the authorities are taking a much stricter line.

"Uefa and Fifa tie in with Wada, the World Anti Doping Agency, and they don't look to distinguish with regards to sanctions between social drugs and performance-enhancing [ones]. There's a general disapproval and that's why there's not a lot of sympathy with the sanctions. [A possible ban] could be anything from six months to two years."