Postecoglou's Samurai Blue benchmark for Asian Cup Socceroos
On Tuesday the men in green and gold tackle the Samurai Blue in Osaka, their final friendly before hosting the Asian Football Confederation's showpiece event in January.
Facing the team ranked second behind top side Iran and nine places above Australia in the region means this will be very far from the morale-boosting formality some teams seeks ahead of a major tournament.
But that's exactly the way Postecoglou wants it.
"It's always a tough game, that's the reason we chose this fixture, particularly away," he said.
"You want to play them at their best. That's what we want to measure ourselves against. It'll be a tough game, but it's what we need.
"Our first mountain to climb is to become the biggest team in Asia. To do that, you've got to measure yourself against the best. I think Japan are number one, we want to become number one. It's not just about the result, it's about the way we perform against them."
While Japan crushed Honduras 6-0 on Friday, the Socceroos have scheduled just one friendly during this international window, with Postecoglou revelling in a chance to drill his players for longer.
"It's been very beneficial," he said.
"Being able to work on our game plan without the pressure of a game in a day or two's time. We've worked hard. And we've got some really meaningful progress in terms of the way we want to play.
"With the Asian Cup just around the corner, every time they train or play is an opportunity for them to cement their spot. Having said that, it hasn't been overbearing. Their concentration and focus has still been on receiving the information we've been giving them."