Following the UEFA Cup tie against Skoda Xanthi on 29 September, Xavier was administered a drugs test and failed. On 23 November 2005, he was found guilty of using the anabolic steroid methandrostenolone (also known as dianabol), and banned from professional football for 18 months. He said that the substance came from anti-virus medicine that he had imported from the United States. While other players had failed tests for recreational substances, Xavier became the first Premier League player to be found guilty of using performance-enhancing drugs. The suspension caused him to miss Middlesbrough's run to the 2006 UEFA Cup final. Xavier remained employed by the club and unsuccessfully appealed the decision; in January 2006 he said that he would take UEFA to the Court of Arbitration for Sport.