"I can't see why we should worry more, we have been preparing for it all this time," the 48-year-old is quoted as saying by Goal.com when asked how the Dutch result had affected preparations.
"We'll have to be much stronger defensively, you saw what their attack did to Spain. But we are at risk if we just think about defending.
"There will be only one outcome if we just do that, so we will also have to do well on attack. Look at Spain. They would have had better luck if they had attacked better. And that's what we should have in mind."
Postecoglou took charge of Australia at the end of last year.