Socceroos captain Mark Schwarzer says a loss or a draw in Tuesday's World Cup qualifier against Oman in Sydney would be a "disaster".The Socceroos go into the clash at ANZ Stadium clinging to second position in Group B in the final round of the Asian qualifying tournament.They need to hang on to that position to qualify automatically for the World Cup in Brazil next year amid fierce competition from Oman, Iraq and Jordan."Anything less than three points will be a disaster for us," said veteran goalkeeper Schwarzer on Wednesday."It's going to be a very, very tough task for us."With three of the Socceroos' remaining four qualifiers to be played at home, Schwarzer said winning each of those was the key."We've ended up being the team that plays three of the first of the four games away, and that was always going to be tough," he said."Obviously, if you look at where we're sitting on the table, it has worked out ok."We would have liked to pick up a couple more points along the way."Now with the four remaining games, every one of them is obviously vitally important, particularly the three home games."Australia, Oman, Iraq and Jordan are locked in a tight contest for the second automatic qualification spot behind runaway leader Japan.The Socceroos head Oman and Iraq on goal difference, with Jordan a point behind.Schwarzer is captain for the clash with Oman in the absence of suspended regular skipper Lucas Neill.