Australia coach Ange Postecoglou was gutted after the Socceroos missed a chance to qualify automatically for the World Cup on Thursday -- leaving their fate resting on next week's game between Japan and Saudi Arabia.

The 2-0 defeat at the hands of Vahid Halilhodzic's men kept Australia third in Group B on 16 points, four points behind leaders Japan, who sewed up their place in Russia with the victory.

Saudi Arabia are second on goal difference by two. If both the Saudis and Postecoglou's men win on Tuesday, Australia need to win big against Thailand at home to qualify for their fourth consecutive finals.

"We're just disappointed we didn't get the outcome we wanted," Postecoglou said. "We just never got control of the midfield the way we wanted to. We had possession but not real effective possession."

"We turned the ball over in transition and they've got the ability to hit you quickly. We just did that too often and brought them into the game. We just couldn't get a hold of that central area the way we wanted to."

"We're obviously in a position where we need to win the game and rely on a result, which is a position we didn't want to be in but that's the position we're in."

The visitors suffered a setback before kickoff, with midfielder Aaron Mooy ruled out for the game after waking up feeling ill.

"Aaron's obviously not well," Postecoglou said. "He didn't have a great night and never recovered, so talking to the doctor, he just wasn't well enough to perform today so we decided to leave him back at the hotel."

As they did in October in Melbourne, Japan sat back on Australia to take advantage of the space behind them, benching big names like Keisuke Honda, Shinji Kagawa and Shinji Okazaki at the start.

"They knew how to exploit us," Asian Cup MVP and Australia midfielder Massimo Luongo said. "They sat back deep and used the spaces behind us. But they did what they had to do. It wasn't pretty but it worked."

The Australian players were visibly and naturally disappointed after tumbling from the brink of qualification to possibly heading to the playoffs, even with a win on Tuesday.

"At the moment, I can't pinpoint it. It's a hard one to take," said Mark Milligan, who deputized as captain in place of the injured Mile Jedinak. "I have no doubt we will regroup and we will put in a wonderful performance on Tuesday night and we'll be fine."

"Japan's a team while they might have been missing some big names, the ones that come in know what's expected of them. They have very good players there."