Australia head coach Michael Cheika expects Saturday's showdown with Wales will be their most brutal match of the World Cup yet.
The Wallabies sealed their place in the quarter-finals by thumping England 33-13 last weekend but their match with Wales will decide who finishes top of Pool A.
The prize for the winners at Twickenham will be a last-eight match with either Scotland or Japan, while the losers will face South Africa.
The stakes, therefore, are high, and Cheika expects a punishing encounter.
Cheika said: "We are still right in the middle of what is pretty much a war zone, our group.
"The goal has been to keep trying to win to get out of our pool, and then go on and keep doing it from there. Saturday will, I feel, be the most brutal game we are going to encounter in the pool.
"It has been physical so far, but my knowledge of tournament play tells me that the further on it goes, the more brutal it gets because the stakes get higher and everyone wants to win more."
Wales have not beaten Australia since 2008, losing 10 Tests on the bounce, while their World Cup record against the Wallabies shows just one win from five.
But Cheika, whose squad trained at Twickenham on Friday with Australian rock band AC/DC's Thunderstruck blaring out on the loudspeakers, has dismissed the fixture's recent history, adding: "It is irrelevant.
"World Cups are different. It is not another Test match. It is one of the few times when you get into tournament play where it is part of a bigger competition.
"It is all about what happens when the two teams front up on Saturday afternoon.
"He (Wales head coach Warren Gatland) is a brilliant coach. With the Lions' victory in Australia in 2013 as well, and what he has done with Welsh rugby over a long period of time, it shows the class that he has got."