The Socceroos' narrow 2-1 win against Thailand just fell short of automatic qualification when the Saudis nicked a lead against Japan to put them ahead on goal difference in the group.

Japan had dominated the first half with multiple chances on goal but, like the Socceroos a few hours earlier, they were denied by goal line clearances and deflections.

In the second half though, the Saudis looked the stronger side and took the lead midway through the final 45, and Japan could find no answer.

A draw or Japanese win would have been enough to send Australia to Russia, but the loss condemns them to a potential globetrotting four match play-off route.

First up will be Syria next month who took thrird spot in the other AFC qualifying group with a last gasp equaliser against Iran to send Uzbekistan crashing out of the running for a World Cup spot.

If Australia can get past Syria over the home and away legs - Syria's home venue has still to be confirmed though as Syria itself is a war zone and no international games are played there – they will face the fourth placed side in the CONCACAF qualifying group stage in November over home and away legs.

The play-offs route could now cost coach Ange Postecoglou his job as Socceroos supremo.

Postecoglou has come in for heavy criticism of his team selections over the past year for favouring players lacking club game time, and more recently for his switch to a back three formation which has left the side vulnerable in defence.

There was speculation earlier in the year that the FFA had lined up Italian coach Gianni de Biasi as a possible replacement if Australia failed to gain automatic qualification to Russia 2018.

In 2005, Frank Farina was fired and replaced by Guus Hiddink on the eve of the historic play-offs against Uruguay, and Postecoglou himself replaced Holger Osieck four years ago despite the German successfully steering the Socceroos to Brazil 2014.

A decision on Postecoglou's future could follow very swiftly after last night's devasting blow to Australia's World Cup campaign.