Ballack was left out of Chelsea's squad for the group stages after the club insisted that an ankle injury would prevent him from being fit.

Ballack has not played since undergoing ankle surgery and the Chelsea medical department maintained that the Germany captain would not be back in time to play any part in the group qualifiers.

Privately, Chelsea insist the midfielder is going nowhere but there are signs of growing impatience on Ballack's behalf after Low revealed the player was at a loss to explain the club's decision.

Chelsea had to name their Champions League squad for their Group B games last Friday but Ballack is hopeful of making a return at the beginning of November.

Now Low has inflamed the situation further by claiming the midfielder cannot fathom Chelsea's reasoning.

Low, preparing Germany for their Group D, Euro 2008 qualifier against Wales, said: "I discussed it with Michael and he could not fully explain Chelsea's decision to me.

"Chelsea's doctors estimate he will not be able to play for two to three more months, but Michael is much more optimistic and expects to play sooner. For us, Chelsea's decision isn't justifiable."

Chelsea and Germany have a history of feuding over Ballack. The Barclays Premier League side were more than unhappy with Ballack's decision to fly home for ankle surgery last May on the advice of German doctors.

The operation ruled him out of Chelsea's crucial UEFA Champions League semi-final against Liverpool and the FA Cup final.

Meanwhile Chelsea defender Ricardo Carvalho says it is important that the Blues get off to a good start in the Champions League.

Although Ballack will not be involved, Chelsea still have to overcome Valencia, Schalke and Rosenborg to reach the knockout stage.

Carvalho, a winner of Europe's top competition with Porto, said: "They are not easy teams to play against, we know more or less Valencia because we played last year, and Schalke are a good team and had a good season. Rosenborg I don't know so much, but the first game is at home so that is good.

"I've been to the semi final twice with Chelsea and had good experiences. Of course I won with Porto, that's my best football moment so far. It's a competition some players can't get, and its difficult to get it, it's a pleasure to have that medal.

"Last season, we didn't have the luck with us because we missed penalties, so let's see. When we start we are thinking about winning the Champions League because it's important for us, but you must have a little bit of luck.

"After 90 minutes in the group stage, if you don't play well you can't go out so you have a little bit of room, you need that.

"It's important in this competition to start winning, at home you have to win and try your best away. The sooner you get the points the better."