Nemanja Matic
Matic returns to Chelsea for £21m.Reuters

Chelsea have signed former player Nemanja Matic from Benfica for a fee thought to be in the region of £21m

The club have confirmed the Serbia international has signed a five and a half year contract at Stamford Bridge just three years after he left west London as part of the deal that saw the Blues sign David Luiz from the Portuguese giants.

"I am very happy for this opportunity to be back at this club," Matic told the club's official website. "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."

His manager Jose Mourinho added: "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, who played against Chelsea in last season's Europa League final, made just three appearances in two years during his first spell at the club following his arrival from MSK Kosice in 2009.

Following his move to Portugal the 25-year-old grew into one of the finest midfielders in the league, helping Benfica win the Taca da Liga in 2012 and earning Portugal's player of the season award last campaign as his side missed out on the league title by a single point.

Having carved a reputation as a formidable yet creative presence in midfield, Matic was also heavily linked with a move to Manchester United. But having indicated last summer that he has "unfinished business" in the Premier League, he has decided to return to Stamford Bridge and could make his debut against David Moyes' side this Sunday.