Jose Mourinho has told Michael Ballack to make up his mind whether to join Chelsea before the World Cup.
Ballack looks headed for Chelsea this summer
The Chelsea boss told Germany's Bild am Sonntag newspaper: "He has got everything. I am impressed by his intelligence on the pitch.
"I have been watching him for a long time. I like him as a human being. But he needs to make a decision before the start of the World Cup."
Ballack, 29, is out of contract with Bayern Munich in the summer.
The club has confirmed they are in "serious negotiations" with the Germany captain.
Mourinho also revealed what Ballack, who was on target in Bayern Munich's 2-0 victory over Bielefeld on Saturday, could expect from a move to England.
"In England we have three matches a week," he added. "That's why we never practice twice a day. Normally we're just playing and travelling. It lets you tire fast."
Chelsea chief executive Peter Kenyon has said he is optimistic they can agree a deal to sign Ballack.
He told BBC Radio London 94.9: "We are at a good stage and I am delighted as to where we are.
"Clearly he is an outstanding and big player so I think we are in good, serious negotiations with him and would echo what he said."
At a press conference in Germany, Ballack said: "Nothing has been decided yet and nothing is signed but I'm in serious talks with Chelsea."
Ballack, who has rejected a new deal with Bayern, added: "At the age of 29 this is my last chance to make a move abroad.
"Chelsea is a top club that is very strong in the league in England and play very, very good in international competition."
Bayern, who lead the Bundesliga, have given up hope of persuading Ballack to stay.
General manager Uli Hoeness said: "From our point of view, it is clear he will leave the club.
"There are no more efforts to keep him. It is a professional situation."
"I am not at all disappointed in him or his behaviour. That is totally normal.
"It is totally wrong to describe us as being angry or anything like that. It is totally the opposite.
"He did wonderfully here and now it is time to get a new club and maybe get more money."
Ballack admitted that he was annoyed at accusations questioning his motives and character.
Hoeness told Kicker newspaper on Monday he believed Ballack was interested in getting acquainted with a "new currency" more than a new language or culture.
President Karl-Heinz Rummenigge had also questioned Ballack's character in big matches.
"I was a bit irritated by the comments from Uli and Kalle in the last few weeks," said Ballack.
"You shouldn't make a move because of the money. It's great to earn so much as a professional soccer player but money doesn't mean anything when you're going about your profession day in and day out. The only thing that counts is sport."