Germany were held 2-2 by Belarus on Tuesday night and Ballack says while intensive training in Mallorca had taken its toll, the side will be stronger when they open their EURO 2008 campaign against Poland on 8 June.
Joachim Loew's side play their final warm-up game against Serbia in Gelsenkirchen on Saturday. "It is not an excuse, but the training camp is very physical, people are tired, but I am sure we will be on form for the beginning of the tournament," said Ballack.
"Against Serbia on Saturday, you will see a different match."
The Chelsea midfielder, who insists he has recovered from the disappointment of losing the Champions League final on penalties last week, added: "When you look at our group, I think we will make the quarter-finals. There are many teams who are a little better than us in terms of technical quality or individual talent, but I believe that our enthusiasm and team spirit can compensate."
Germany are drawn with Poland, Croatia and co-hosts Austria in Group B.