Chelsea have signed Senegal international defender Papy Djilobodji from Nantes on a four-year contract, according to a statement on the French Ligue 1 side's website.
Financial terms of the deal were not disclosed but British media reported that the clubs had agreed a fee of about 2.7 million pounds ($4 million) for the 26-year-old.
Djilobodji has made 59 top-flight appearances for the French side and scored three goals.
Chelsea, who sit in 13th place in the Premier League, have conceded nine goals in their four matches so far this season, one less than Sunderland who sit bottom of table.
Manager Jose Mourinho made Everton and England defender John Stones his number one target but the Merseyside club staved off every offer the champions made for the 21-year-old central defender.
($1 = 0.6512 pounds)
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