Despite conceding only once in their opening two matches, the Bayern Munich shotstopper believes that they can be more economic at the back for the games against Republic of Ireland and Sweden.
"We have to concentrate more, that is very important. We have got many great attacking players, but we can not disregard the defence," the 26-year-old told TZ.
"In my opinion it is important to have a stable defence. [Miroslav] Klose is the best example. His defensive qualities as a striker are outstanding."
Die Mannschaft are currently top of Group C with six points from two games.