The Black Cats are believed to be keen on seeing the back of the Uruguayan.
Much of Sunderland's activity this month has seen them trying to get players out of the club.
Costel Pantilimon has headed to Watford whilst the likes of Danny Graham, Will Buckley and Liam Bridcutt have all been loaned out to the Football League.
Now it seems another player may be cut from the squad by Sam Allardyce.
The player in question is Uruguayan international Sebastian Coates.
Sunderland are reportedly ready to let him exit the Stadium of Light this month and are even in talks with a potential buyer, according to the Shields Gazette.
They claim that Sunderland have opened negotiations with Sporting Lisbon regarding his departure.
They are open to the idea of loaning out Coates until the end of the season before seeing him join the Portuguese giants on a permanent deal.
The move comes as a surprise as Sunderland only signed the player permanently in the summer from Liverpool.
But that was a deal brokered by his countryman Gus Poyet and Allardyce is clearly not as keen on the defender.
Coates has struggled this season and has not played for the club since the 3-1 FA Cup defeat to Arsenal earlier this month.