Chelsea have completed a contract worth £ 21 million with Benfica midfielder Nemanja Matic, for five and a half years.
The 25-year-old player left Benfica to Chelsea three years ago.
"I am very happy with this opportunity. I just want to say will give their best to help the team and make the Chelsea fans happy," said Matic.
Mourinho has signaled eyeing midfielder as his main target when moving to Stamford Bridge and would not mind returning to recruit players who left the club.
Serbian national team player transfer value is about £ 5 million when he left Chelsea there in January 2011 as part of the agreement for the merger of David Luis from Benfica to Chelsea.
Chelsea closing some transfer value Matic Kevin De Bruyne to release to Wolfsburg for £ 16 million.
In addition Matic and Luiz, Chelsea also recruit Brazilian midfielder, Ramires from Benfica in 2010 with a value of £ 17 million.
