"The door of Real is not closed for Michael, his footballing qualities are always there, they will still exist in six months, but it is essentially a question of money," the German tactician told German sports magazine Kicker.

Ballack left Bayern Munich on a free transfer in 2006 and only Chelsea could afford his wage demands.

Schuster said that there were negotiations with the Blues midfielder this summer but the deal collapsed as the 30-year-old midfielder refused to reduce his wage.

"He has an extraordinary contract at Chelsea, such a deal would have exploded our budget. No player at Real is paid like him and we do not want to set a precedent," added Schuster.

Ballack is reported to be on a move out of Stamford Bridge especially after being dropped from Chelsea's Champions League squad.

The Blues have issued a statement confirming that his name was omitted as his injury will keep him out for a long time.