The Roar have not beaten United in three Queensland derbies so far but Postecoglou wants the fans to get behind their team and help them to a positive start to the season.
"We'll have quite a few supporters come down to the Gold Coast and it will be a good atmosphere," Postecoglou said.
"There was a rivalry built up last year and we want to build on it this year for sure.
"The derby game should mean something more, it certainly means something more to our supporters.
"I don't think we can sit there and say: 'The reality of it is you do only get three points, you don't get six points for it'.
"For us, coming off a really disappointing season last year and knowing our next game is a home game against Sydney, we've got a real chance to give something for our supporters to be optimistic about."
The Roar meet Gold Coast at Skilled Park on Sunday - kick-off is at 3:00pm.