Carlo Ancelotti has turned down the chance to return to AC Milan, telling the club he needs rest.
Jose Mourinho insists Diego Costa is content at Chelsea in response to reports linking him with a return to Atletico Madrid.
The 28-year-old has joined the club from Internacional for an undisclosed fee and has signed a two and a half year deal.
He becomes Gus Poyet's fourth acquisition this month following Spanish full-back Marcos Alonso's arrival on loan and the captures of Scocco's compatriots Oscar Ustari and Santiago Vergini.
Scocco was in the stands at the Stadium of Light as the Black Cats beat Stoke 1-0 to climb out of the Barclays Premier League relegation zone.