Chelsea have confirmed the signing of Nemanja Matic from Benfica.
The midfielder has agreed a five-and-a-half-year contract and returns to the club for a fee of around £21m.
Serbian Matic, 25, left as part of the deal that took David Luiz to Stamford Bridge from Benfica in January 2011.
“I am very happy for this opportunity to be back at this club,” he said.
“I feel very good because of that and just want to say I will give my best to help the team and make the Chelsea fans happy.”
Manager Jose Mourinho said: “I am very pleased that Nemanja is returning to Chelsea.
“He has grown as a player in Portugal and has become a fantastic all-round midfielder.
“I am sure he will become a very important member of the squad and help us to achieve our ambitions.”
Matic will wear Chelsea’s number 21 shirt.