The German midfielder is battling to be fit for the visit of Reading on Wednesday night after a calf strain kept him out of both the Carling Cup semi-final second leg win over Everton and the FA Cup victory at Wigan on Saturday.

After recovering full fitness following ankle surgery, the 31-year-old has taken a leading role in Avram Grant's side, which has been without captain John Terry and fellow England international Frank Lampard because of their own injury problems.

Former Bayern Munich midfielder Ballack, who arrived at Stamford Bridge after the 2006 World Cup, has more than two years left on his current deal and rejected any suggestions he could be set to move on after now having finally settled into the English game.

"At the moment I am completely happy here," Ballack said German newspaper Suddeutsche Zeitung.

"My family and I have adjusted to life in England, I have a contract, and no desire to switch clubs.

"I am playing for a great team and hope to achieve great things."

Ballack added: "What comes when my contract expires, we'll just have to see.

"Whether I stay another year, go somewhere else of hang up my boots - you never know in football."

There was, meanwhile, a surprise visitor to Chelsea's Cobham training complex today, when Argentina legend Diego Maradona paid an unexpected visit.

The 47-year-old - whose infamous 'Hand of God' goal knocked England out of the 1986 World Cup in Mexico - spent some time chatting to Blues manager Grant as well as Ballack, striker Andriy Shevchenko and Chelsea's new Argentinian youngster Franco Di Santo.

"In the world of football he is a hero for every player, he is an incredible player," said Shevchenko, who has returned to training following a back problem.

"He is a legend, a hero for everyone, and a fantastic player. He has had a difficult life, but he is doing well now. His look is good and it's important for him.

"He has lost a lot of weight, and feels much better."

New signing Branislav Ivanovic also joined in with training to continued his progress towards match fitness.

Chelsea have been installed as new favourites for the FA Cup following today's draw for the fifth round, when they were handed a home draw against League One side Huddersfield, while Barclays Premier League pacesetters Manchester United and Arsenal were paired together.