Sunderland completed an £8 million deal to sign centre-back Papy Djilobodji from Chelsea on Friday night.
The 27-year-old becomes David Moyes' first signing at the Stadium of Light since being appointed manager two weeks ago.
Djilobodji, who inked a four-year deal, only played a few seconds of a competitive match in a Chelsea shirt, at the end of a League Cup game last September.
He joined Werder Bremen on loan in January, scoring twice in 14 Bundesliga games, including a crucial late winner that ensured they avoided relegation on the final day of the season.
However, despite his minimal impact at Stamford Bridge, Chelsea have trebled their money on a player who has been capped 13 times by Senegal and appeared at the 2015 African Cup of Nations.
"Chelsea Football Club thanks Papy for his service and wishes him well for the future," said a statement on the London club's official website.
Djilobodji began his career in Senegal with ASC Saloum before joining French club US Senart-Moissy in October 2009. He joined Nantes in 2010 and went on to make 171 appearances, scoring nine goals across five years.