Louis van Gaal's side started their campaign by cruising past the defending champions last Friday, but De Jong believes that there can be no room for complacency against an Australian side desperately looking to keep their hopes of reaching the knockout stages alive.
"I understand that the euphoria is very large after the 5-1 against Spain, but we have to give everything against Australia," the 29-year-old told reporters.
"Of course it was a fantastic victory but it is only a group match. We have achieved nothing yet. We are going to focus on the game against Australia."
The Socceroos are looking to recover from a 3-1 defeat to Chile.