Sunderland are facing a potential legal battle with Inter Milan regarding the future of winger Ricardo Alvarez, according to a report.

The Argentine was signed on a season-long loan deal by the Black Cats last year but struggled to make an impact during his time at the club, while a knee injury ended his campaign in March.

Alvarez was expected to return to Inter following his loan spell, but the Serie A side believe that he is now a Sunderland player due to the terms of the deal that sent him to the Stadium of Light.

The Black Cats reportedly agreed to buy the 27-year-old for £7.5m if they remained in the Premier League, but are now claiming that Inter's refusal to allow them to treat Alvarez's knee injury has voided the permanent move.

Roberto Mancini's side are taking the matter to FIFA to resolve the dispute, who will decide through arbitration the player's future, reports the Sunderland Echo.

Alvarez made 17 appearances for Sunderland last season, scoring one goal.