The Dutch club are still insistent they have a pre-contract agreement with the striker, a claim which is disputed by Alves. The 27-year-old was sold by Heerenveen to Boro for an undisclosed fee on transfer deadline day but AZ chairman Dirk Scheringa will ask FIFA to investigate.
He told De Telegraaf: "He really has a chance of getting banned from playing for the rest of the season. We have a water-tight contract with him."
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