A drought-breaking win over the Asian powerhouse would all but assure Australia an automatic berth in next year's World Cup in North America.

The Socceroos have a three-point lead and a significant goal difference advantage over Saudi Arabia as they jockey for second place in Group C of Asian qualifying.

But a loss or draw against already qualified Japan means Australia will be thrust into a critical clash against Saudi Arabia in Jeddah on June 10.

A win does not totally guarantee Australia's passage if Saudi Arabia claim victory in their away game against Bahrain later on Thursday.

"We just need to finish the job off. We can take a major step tomorrow night by winning," Popovic told reporters on Wednesday.

"There's a real excitement from the group, but there's a calmness and confidence in our ability."

Australia have not beaten Japan since 2009, but hopes are high against a considerably weakened side resting a slew of top players.

Leeds United star Ao Tanaka, Reims forward Junya Ito and Hidemasa Morita from Sporting Lisbon are among the players missing for the Samurai Blue.

In contrast, Australia will boast a near full-strength side and buoyed by the recent return of Parma defender Alessandro Circati from a torn anterior cruciate ligament.

"It's been a long time since Australia has beaten Japan, but I have a lot of confidence in this group," said Popovic, who has turned Australia's fortunes around since replacing Graham Arnold in September.

"At some point, Australia will beat Japan. We have a chance to do that tomorrow and we want to take that opportunity."

A febrile atmosphere is tipped with 50,000 fans expected to attend Optus Stadium despite stormy weather in Perth ahead of the game.

"We certainly are aware of what these games mean to us and mean to Australia," Popovic said.

"I'm very confident the players will go out there and execute in a very calm, composed manner."

With an eighth straight World Cup appearance assured, Japan are using their trip to Australia and subsequent home game against Indonesia as an opportunity to trial younger players and build depth.

Japan's 27-man squad includes eight uncapped players, but Liverpool midfielder Wataru Endo and Real Sociedad's Takefusa Kubo provide plenty of class for the Asian nation eyeing a first World Cup triumph.

"The ultimate goal is to win the World Cup," Japan coach Hajime Moriyasu said.

"So we really need to take each match and the time we prepare for matches seriously.

"We need to build the strongest team possible (for) the World Cup."