The Wallabies were belted and bloodied during their thrilling semi-final win against Argentina 29-15 at Twickenham on Sunday (Monday morning AEDT), and they gave as good as they got as a brutal game took a physical toll.

Pocock looked to have broken his nose just 15 minutes into the game and blood started to pour down his face. But the flanker, making his comeback from a calf injury, continued to put his head in dark places to win the ball at the breakdown.

Scott Fardy joined the claret brigade when he was opened up in the second half, Bernard Foley had blood coming from a cut on his ear and Argentina fullback Joaquin Tuculet had cotton stuffed up his nose to stop it bleeding.

It showed what was required for the Wallabies to book their ticket to the final and a showdown with trans-Tasman rivals New Zealand in the biggest game between the countries since the last World Cup.

Pocock wiped the blood from his face after the match, but his eyes were puffy after being whacked in the nose.

An injury cloud hovers over Matt Giteau, who left the field with a groin problem in the second half while Israel Folau (ankle) also failed to complete the match.

It is also hoped prop Scott Sio will recover from an elbow injury in time to return to the starting side to battle the All Blacks' scrum.

The Wallabies scored four tries to nil and made an amazing 142 tackles to hold on for victory thanks to an Adam Ashley-Cooper hat-trick.

But it was the blood they spilled during the contest which shows the desperation is back in the Wallabies side a year after Australian rugby was in turmoil.

"It was incredibly tough, credit to Argentina. It was exactly what we thought it was going to be," Pocock said when asked how physical the match was.

"It was physical and both teams used the ball, right until the 80th minute. Everyone was out on their feet but we were working hard.

"I thought there were a few pieces of finishing from the back line and that was pleasing. But after that it was a pretty tough contest around the park - the set piece and the ruck was a target area for both teams. It was a pleasing win."

Pocock was immense in his superb return from injury.

Despite needing constant attention from Wallabies medical staff, Pocock made 13 tackles and effected four turnovers at the breakdown.

To get an idea of how physical the match was, Australia made more tackles than they did in their pool match against Wales, which was widely lauded as the most courageous defensive effort in Wallabies history.

In that match the Wallabies made 134 tackles and played with just 13 men on the field at one stage to hold on for a crucial victory.

But against Argentina, despite the effects of seven weeks at the World Cup, they picked themselves up to make their 142 tackles.

In comparison, Argentina made 95 tackles.

The Wallabies got off to a perfect start when Rob Simmons latched on to an intercept after just one minute and 13 seconds, scoring the fastest try of the World Cup so far to give Australia an early lead.

Ashley-Cooper scored a hat-trick thanks to some good lead up work from his inside men, and his last try was courtesy of a superb Drew Mitchell run that beat eight defenders before getting the ball to Ashley-Cooper.

Argentina were in the wars as well, losing winger Juan Imhoff to concussion and captain Agustin Creevy to a leg injury before half-time.

Tuculet had blood coming from his nose for almost the entire match, but medical staff stuffed cotton wool into his nostrils so he could stay on the field.

The challenge for the Wallabies is to regroup and re-energise in time to play against the All Blacks in the final.

Australia and New Zealand have never played in a World Cup final, but share a rich Bledisloe Cup history. They have played twice this year with each team claiming a win apiece.

"What is important for me to say is that I'm a massive fan of the Argentinians and the way they play the game," said Wallabies coach Michael Cheika.

"It was a good shift [in the back row of Pocock, Fardy and Michael Hooper]. They work really hard for the team. They pick the moments to go ... David, off the back of his injury was a great effort.

"New Zealand will be feeling pretty good. We've beaten them something like one in the last 10, so they'd be feeling pretty good. They've got our measure. It's up to us to do something special."