The Wallabies' set piece went backwards for the first time in the tournament, conceding four penalties as Australia held on to beat Argentina 29-15 in the semi-final on Sunday (Monday morning AEDT). But captain Stephen Moore is confident the forward pack can work out the kinks to get back on track for a blockbuster final against New Zealand at Twickenham on the weekend.

Sio faces a race against the clock to return to the starting side after an elbow injury kept him out of the tense win against Argentina. The fact the Wallabies opted against sending him back to Australia last week indicates medical staff thought he could recover in time to play in the final if they advanced to the last game of the competition.

However, the Wallabies have a short turnaround and just five days to prepare to for the final.

There were some worrying signs for the Wallabies at scrum time as Argentina put the pressure on and managed to win four penalties.

In the past two Tests, the Wallabies have conceded seven scrum penalties compared to just six penalties in their first four matches of the World Cup.

They started the tournament as an under-rated pack which wasn't expected to cause any trouble for England, Wales or any other team with a good set piece. But now they have to prove they can fightback to build on the respect already gained.

"[Argentina] certainly scrummaged well and we had our challenges at times. That's the way some of these games go," Moore said.

"We know Argentina have a very strong scrum and that's the way it went on a few of these scrums ... but I think the guys that were out there sorted it out, that's all you can do.

"We're certainly not sitting back and looking at anything we've done. We're taking each game as it comes ... we know [the scrum] is going to be an important part of the game and we need to work hard on it to make sure it can function well."

Sio will have until Thursday (Friday AEDT) to prove his fitness as the Wallabies rest some wounded bodies in the build up to the final.

Matt Giteau came off with a groin strain while Israel Folau left the field late in the second half after making his comeback from an ankle injury.

The Wallabies have been toiling away for five weeks, bashing each other at training and then recovering in time to do the same to their opponents in the group of death and now the finals.

The Wallabies were locked in intense slogs against England and Wales before escaping in the quarter-final against Scotland and then running into a fired-up Argentina side in the semi-finals.

On the other side of the draw, New Zealand cruised passed Namibia, Georgia, Tonga and France before a tight tussle with South Africa in the semi-final.

Asked how much his players had left in the tank, Wallabies coach Michael Cheika joked: "Probably about 80 minutes, I reckon.

"We might need a little more, you never know. Obviously New Zealand have had a very different path to us to here. They'll be feeling a little bit differently in their preparation.

"But it's a World Cup final and the adrenaline's going to be pumping and I think anyone who's a little bit sore is going to forget all about soreness when that whistle blows."