Jose Mourinho talks up Diego Costa

Chelsea manager Jose Mourinho says that the quality being displayed by his summer signing Diego Costa has surprised some of his new teammates.

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Costa became Chelsea's most expensive purchase of this transfer window when he arrived from Atletico Madrid for 32 million pounds, and Mourinho is impressed by what he has seen from the Spain striker in his first few weeks at the club.

"He's a great addition for us," Mourinho told Sky Sports. "He is a fantastic player. Technically he is very, very good. That's why lots of the players are so happy and so surprised, because his quality is even higher than what they expect.

"He's so strong physically and gives so much effort during matches. He's a great addition for us. He's a fantastic player. When somebody sees him play the first thing that gets into their eyes is exactly that, the capacity to work hard for the team."

Mourinho went on to suggest Cesc Fabregas will be asked to fill a variety of roles at Chelsea this season, with his ability to play as a holding midfielder and in creative No. 10 role exciting the Chelsea boss.

With Oscar and Willian among those joining Chelsea's training camp late after their World Cup exploits this summer, Mourinho is relishing the versatility Fabregas is offering him.

"In this moment without Oscar and Willian, players who have more conditions to play as our No. 10, we are using Cesc as a No. 10. I also see him as a player who can play [deeper] in a pivot role.

"I see him as somebody who thinks football faster than the majority of the players. He is the kind of player we need in our midfield to bring us to a different dimension.

"The ball possession, the speed of the circulation, the decisive pass. He has everything."

Mourinho went on to confirm that the move to allow veteran performers Ashley Cole and Frank Lampard to leave Chelsea this summer was "a joint decision", as he suspected they would not be content warming the bench.

"We arrived at a moment when we decide what is best for the team, what is best for the other players and what is best for them," he added, in a summer that has seen Cole join Roma and Lampard sign a deal to play for New York City in the MLS in 2015.

"It depended on their mentality. If they were the kind of guys who were ready to be in the club with another profile and accepting the evolution, that we want to bring the young players in and build for the future, maybe. But they are not this.

"Lampard and Ashley will be to the last day players who want to compete and play in every game, to be involved. They are happier in this new situation, even though they both love Chelsea. My last message to them was to be happy and come back one day [to Chelsea] in a different role."

Lampard is expected to join Manchester City on a half-season loan with the New York City franchise not yet active.