Sunderland have signed Santiago Vergini on loan from Buenos Aires club Estudiantes.
The 26-year-old arrived at the Stadium of Light last season for a loan spell that saw the Argentine make 16 appearances.
Vergini told the official club website: "I'm very happy to be here once again.
"The challenge for me is to become part of this team and offer all I can."
Vergini becomes Gus Poyet's sixth summer signing, after the arrivals of Jack Rodwell, Costel Pantilimon, Jordi Gomez, Billy Jones and Patrick Van Aanholt.
The central defender has made just one appearance for the Argentina national team.
