Yet at the same time says he feels "alive". And why wouldn't he be?

Australia's 80-minute quarter-final performance against England on Saturday in Oita will be the polished product of four years of planning and the only thing that really matters when it comes to gauging if this Wallabies team under Michael Cheika the regime are World Cup contenders or pretenders.

Players will try to put it to the back of their minds but that now that sudden death is upon us, the stakes are higher than they have been across a World Cup cycle in which the Wallabies have won 23 of their 51 Tests (45 per cent).

Hooper is a relaxed character and appeared so at his media conference on Friday in front of the world's media. So too is Jordan Petaia; the teenager with pizzazz and enough praise already in his short career to make anyone feel a little sheepish.

But this is a World Cup quarter-final and given players tend to spit out the party line that these are no different to others, it was nice to see the Australian captain delve into how he was feeling on the eve of a blockbuster clash.

"I'm nervous," Hooper said. "But that's good, it means you care. I was nervous the first Waratahs game of the year, the first trial and I'm nervous now. It's part of being a rugby player. You feel alive and ready to go.

"It's not a normal week. It's a quarter-final and that's great. How good is that - to be here and in this position with this opportunity.

"Tomorrow is a complete unknown. We're feeling good, we're ready."

Given that Hooper has a World Cup final on his CV, imagine how others will be feeling when they run out onto Oita Stadium in front of what is expected to be a sea of gold and white.

In less than 24 hours, the landscape and narrative around Australian rugby could be profoundly different. If Australia can defy odds, expectations and a six-game losing streak to topple an England side yet to drop a game at the World Cup, it would be a tremendous achievement and get them to what most believe is a pass mark; making a semi-final.

A loss? Michael Cheika will likely walk away. His assistants would therefore be unlikely to stick around. The likes of David Pocock, Will Genia and Sekope Kepu no longer in a gold jersey, not to mention the likes of Samu Kerevi and Adam Coleman who are departing Australian rugby shortly to earn some yen and pounds.

Players and coaches have given little away this about their tactics or even deep analysis on their opponents, who have not made a World Cup semi-final since 2007.

Australia's trend of poor seconds halves against England suggests they need to start well and cannot be trailing at half-time. Hooper said being in a position to strike late was important and admitted the Wallabies had not started matches as well as they would have liked at this tournament.

"I am starting to be of the belief that starting well is preparing you well for the back-end of the game when it opens up a bit," Hooper said. "[It is about] starting well and sticking to your principles early, not getting flustered by things that are happening and not getting flustered by the scoreboard because you don't win the game at half-time.

"[We want to be]confident with whatever comes at us throughout that period."

Hooper's job is to try and settle the nerves of Petaia, whose selection at No.13 - a position he has never played at Test level - has generated no shortage of debate. Everyone is willing him on to do well but if England centres Manu Tuilagi and Henry Slade have the potential to make the wide-eyed Queenslander's afternoon a nightmare.

"Got a lot of confidence in Jordy dropping into that position," said Wallabies defence coach Nathan Grey. "Like all things defensive, it's a team effort so that collective effort is going to be really important."

Hooper is a captain who leads by example and incredibly passionate about his country. So too is David Pocock, and many other players, but in these two back-row bandits the Wallabies have a couple of genuine game-changers that England will have done plenty of homework on.

The skipper acknowledged the breakdown was going to be a significant part of the match and said he felt there had been some inconsistencies with how referees police defensive players trying to win the ball back.

Frenchman Jerome Garces has the whistle for this match and it is critical Hooper and the Wallabies maintain their discipline.

"I've observed the ruck being refereed in a multitude of ways, not any one way in particular, so it has made it quick tricky there," Hooper said. "The breakdown, turning the ball over, winning your own ball is a team effort from [number] one to 23. How we start the game and definitely adapt to what's going on out there is pretty crucial for us."