Friday's SheBelieves Cup opener in Houston, against Asia's top team, was meant to be an ideal litmus test just over a year out from the tournament.
Instead, the Matildas' heaviest ever defeat to Japan should ring alarm bells for Football Australia, who are still to appoint a permanent head coach.
Interim coach Tom Sermanni fielded a full-strength team, bar Sam Kerr, clearly with high hopes.
But in a horror first half against the world No.7, it quickly became clear just how much work the Matildas have to do.
Defensive mix-ups allowed Mina Tanaka to score in the fifth and 32nd minutes and leave Australia shellshocked.
Tanaka turned provider for Maika Hamano in the 52nd minute, before Moeka Minami headed home in the 75th to seal a dominant victory.
Australia registered one shot to Japan's 18, including eight on target, as they were overwhelmed by an ominous Nadeshiko.
The Matildas struggled to get in-form Manchester City gun Mary Fowler involved and struggled to keep a foot on the ball.
But most concerning was a lack of connection in an experienced defence - Steph Catley, Clare Hunt, Alanna Kennedy, Ellie Carpenter plus goalkeeper Mackenzie Arnold.
Poor organisation allowed the Nadeshiko to draw first blood.
Under little pressure, Aoba Fujino whipped in a cross and a poor clearing header from Catley failed to avert the danger.
Fuka Nagano trickled a weak shot towards Tanaka, who jostled with Kennedy and backheeled the ball between the defender's legs.
Tanaka smacked a free header off the crossbar in the 26th minute.
In the 32nd minute, chasing a long ball, Hunt cut across Kennedy, leaving Tanaka open to slide in and score.
Some sublime passing seven minutes after the break pulled Australia's defence apart, before Tanaka's low cross teed up Hamano for a simple tap-in.
Arnold made a big save to deny Riko Ueki in the 62nd minute and Sermanni turned to his bench two minutes later.
Holly McNamara, earning her first cap since the 2022 Asian Cup, Daniela Galic, Winonah Heatley and Charli Grant replaced Caitlin Foord, Fowler, Kennedy and Catley.
Japan completed the rout from a short-corner routine.
Yui Hasegawa nudged the ball to Kitagawa, whose wonderful cross was beautifully flicked home by Minami.
Charli Grant smacked the crossbar with Australia's first shot in the 87th minute.
Australia play the United States in Glendale on Monday (AEDT) before meeting Colombia in San Diego on Thursday.
