Sunderland are braced for a £10million payout on a player they do not own.
Loan flop Ricky Alvarez was sent back to Inter Milan at the end of the 2014/15 season despite a contractual obligation to buy the Argentina winger should they avoid relegation.
The Black Cats claimed Inter had hesitated over a knee operation Alvarez needed and said the Italian club were in breach of the agreement.
FIFA subsequently ruled in favour of Inter but Sunderland appealed and the Court of Arbitration for Sport (CAS) is now set to deliver a final verdict on the saga.