What happens if Australia doesn't win?

It all goes on the line at the Olympic Stadium in Sydney tonight, and not just for Australia.

In many ways the Socceroos match with Iraq is also the biggest game in Oman's football history, as the outcome at Homebush will determine their World Cup fate when they kick off against Jordan several hours after the Australia-Iraq match is finished.

An Australian win, and the best the Omanis can hope for is third place.

But should the Socceroos falter and draw or lose, then Oman's fate will be in its own hands.

An Australian draw or defeat with Iraq would leave the Socceroos on 11 or their current 10 points, meaning Oman would move to 12 and take the automatic second qualifying place for Brazil if it can win in Amman.

A draw with Jordan would not be enough even if the Socceroos lose, as Oman and Australia would both be on ten points, but Australia's goal difference is far superior.

Its a pretty big deal for the Jordanians, too, as they could still clinch third place by beating Oman, keeping their hopes of World Cup qualification alive through the playoffs.

Their dreadful goal difference means they don't have a hope of finishing in second spot, even if Australia lost to Iraq and Jordan beat Oman to finish on 10 points with Australia.

Mathematicians and statistical buffs might argue the toss, but they would have to win 10-0 and the Socceroos go down 0-5. Its not going to happen. This is one night where the improbable won't become the impossible.

The most likely outcome is that Australia will get the result it needs and Oman, which has had a good record on the road in these qualifying games - in part due to the skills between the sticks of their redoubtable goalkeeper Ali Al Habsi, who has spent several years in the English Premier League - will get the point it needs to take third spot.

If it does all go pear shaped for the Socceroos tonight all is not quite lost, as the long distance route through the playoffs remains an option.

But if there is light at the end of the tunnel, it is an extremely long tunnel, involving long and arduous trips through Asia and Latin America.

The other Asian group is also going down to the wire but the odds are that South Korea and Iran might manage to draw with each other when they meet in Seoul as that is a result which would probably ensure both qualify in the top two spots.

The Koreans are effectively in Brazil anyway, as the best the third placed Uzbekistan can do against them is match their 14 points if they beat Qatar and the Iranians win in Seoul. South Korea's goal difference, at plus seven going into this game, is far superior to Uzbekistan's plus one.

For the Uzbeks to displace the Iranians they need to beat Qatar and South Korea to beat the Islamic Republic.

If the Koreans and the Iranians draw by any score less than 3-3 they would need to beat the Qataris by something like four clear goals to finish level on points (14) and goal difference with Iran but progress on goals scored. Not impossible, but unlikely.

The identity of the third placed team would matter for the Socceroos if they did stuff up, as that team would their first playoff opponent.

Australian failure tonight would in all likelihood see them having to beat the Uzbeks home and away before progressing to a final intercontinental showdown with the fifth-placed South American side. If its not the Uzbeks it would be the Iranians.

That back to the future scenario could become even more eerily scary if the fifth placed team turns out to be Uruguay, as it has been twice in the past.

With three games remaining Argentina look nailed on for top spot in the South American qualifying section.

Colombia has four matches left, and seems home and hosed for a top four finish, as does Ecuador, which always racks up points at home because of the advantage it gets playing at high altitude in Quito.

Uruguay is currently fifth, five points behind Chile but with a game in hand. Venezuela and to a lesser extent Peru could also be in the mix for fifth spot, although it is hard to see the two last placed teams, Bolivia and the previous regular qualifiers Paraguay, regaining lost ground.

Brazil, as hosts, are automatically there.

So Socceroos fans should brace themselves: get it wrong tonight and the nightmares of the two previous decades - World Cup trips to Tehran and Montevideo - could loom in the short term future.

• Australia can qualify Directly to Brazil with a win.
• If the Socceroos finish third they will face an Asian play off against Uzbekistan or Iran.
• If they win that they will likely meet Chile, Uruguay, Venezuela or Peru in an Asia v South America final qualifier