Sunderland have loaned defender Sebastian Coates to Sporting CP as Sam Allardyce's January overhaul of the Black Cats continues.
Sporting will take Coates for the remainder of the season and a statement from the Portuguese club revealed they have agreed a EUR5million fee to make the move permanent at the end of the campaign.
Coates has played 32 times for Sunderland since arriving, initially on loan, from Liverpool in September 2014.
The Uruguay international had played in 12 of Allardyce's 16 games in charge of Sunderland, although he has been out of the side since their FA Cup third-round defeat to Arsenal, subsequently missing three Premier League games.
Defenders Jan Kirchhoff and Lamine Kone have arrived at the Stadium of Light this month as Allardyce looks to drag the Wearside club out of the relegation zone.
Sunderland sit second from bottom in the table, four points from safety with 15 games to play.
Coates will swap a relegation fight for a title challenge with Sporting, who top the Primeira Liga by two points from local rivals Benfica.