However the FFA revealed on Saturday night that Cahill had escaped an ankle fracture. A further update would be issued on Sunday.

Melbourne City marquee man Cahill limped off the field early in Friday night's 1-0 defeat to Sydney FC at AAMI Park after rolling his ankle following a collision with Sydney defender Jordy Buijs.

The veteran striker grimaced with pain, knowing immediately that he was in trouble.

An FFA statement on Saturday said Cahill has X-rays on Friday and an MRI scan on Saturday "to determine the full extent of the injury".

"While no fracture was identified, monitoring and rehabilitation will be required to manage Cahill back to full fitness," the statement read.

Cahill tried to get up and walk the injury off on the sideline but admitted that he had to leave the arena, subsequently going off to hospital on Friday night.

He had more scans on Saturday morning, but so far the results appear to be inconclusive on what the injury is/

An FFA spokesman said on Saturday afternoon that Cahill was still being attended by City's medical staff, who were liaising closely with the FFA's own medical professionals.

"A decision will be taken on Sunday after the swelling subsides," he said

"We won't really know until then what the real situation is."

Cahill's cause is not helped by the fact that the first leg is in Honduras, as a 30-hour travel time with such an injury would clearly not help it heal.

The sensible decision, if officials are not confident that he will be 100 per cent fit, would be to leave him at home in Melbourne to recover fully so that he is fit, rested and ready to play a major role in the second leg, in Sydney on November 15.

Cahill may be nearly 38 but his importance to the Socceroos cannot be underestimated.

The former Everton man is Australia's leading goal scorer and showed how essential he still remains in the playoff against Syria in October.

He got Australia's first-half equaliser after the Syrians took a shock early lead, then popped up near the end of extra time to head home the crucial winner.

His teammate and club captain, Michael Jakobsen, said much would depend on Cahill's powers of recovery.

"I'm not a doctor, it depends on your body and how hard you twist your ankle," Jakobsen said. "He could train tomorrow with a good strapping, who knows, so I can't say specifically how he can recover from it.

"There's no doubt he brings a lot of energy and experience. It's a big loss when a guy like that goes off. During the week and in the warm-up he looked sharp."

Australia has been here before, but with the boot on the other foot.

In 2001 Uruguay left their main striker, Dario Silva, at home in Montevideo and did not bring him to the first leg of the intercontinental playoff in Melbourne, which Australia won 1-0, thanks to a Kevin Muscat penalty.

But Silva was very much available for the second leg and scored Uruguay's first goal early in the game to make the tie 1-1 on aggregate. Richard Morales added two more in the final 20 minutes to make the score 3-0 to Uruguay on the day, and 3-1 on aggregate, ensuring the South Americans went to the World Cup in South Korea and Japan in 2002.

The Socceroos got their revenge four years later in that dramatic playoff penalty shootout win in Sydney, going on to progress to the last 16 of the tournament in Germany.

Sydney boss Graham Arnold admitted after the game on Friday that he was not expecting Cahill to line up against the champions.

"I was actually surprised he started, I thought he was going to be away for the next few weeks, but I don't make those decisions," Arnold said after the match.

"At the end of the day, as a coach, I probably would have planned a bit different because he wasn't going to be here for the next three weeks anyway [but] it's not my choice, it's Warren's [Joyce, coach].

"The first thing I thought of straight away was the national team. Timmy's our star, you can't give too much credit to someone who does so much for the country.

"What he did against Syria, 120 minutes, what he did was phenomenal. Let's all keep our fingers crossed he's OK."