The 3-0 victory over the European minnows in Hannover was much tougher than many predicted, and Flick cannot see his side overcoming Austria with a similar performance.
"Our wastefulness in front of goal was probably the only thing we can complain about," Flick told reporters at a press conference.
"Otherwise we have to compliment the team. They have implemented much of what we planned, and against a team defending so passionately, it is always hard."
Austria, however, will present a much sterner test for Germany and the 47-year-old is well aware of the potential danger ahead.
"[Marcel] Koller gave their game a system," he added.
"They defend well and switch fast to the attack. With [Martin] Harnik and [Marko] Arnautovic they have very good players in the attack. It will be hard and we need to be consistent."