premise: Middlesbrough defender Abel Xavier has again tested positive for a banned substance in the B sample of his original test, a UEFA spokesman said on Tuesday.
  The spokesman said: "The B sample has confirmed the original findings."
  The 32-year-old, who was tested after Boro's UEFA Cup game at Xanthi, is set to face a Uefa hearing on 17 November and could be banned for a year.
  Xavier has denied any wrongdoing and said last month: "I am convinced there is a harmless explanation."
  And the Portuguese star has been suspended from all competitions while an investigation takes place.
   Why has Xavier been suspended from all competitions?
hypothesis: a Uefa hearing