LONDON: The Wallabies have found an unlikely ally in Wales coach Warren Gatland, who has backed Australia to beat England and guarantee his team a place in the quarter finals.

Gatland threw his support behind the Wallabies after Wales secured a crucial win against Fiji in Cardiff on Thursday night (Friday morning Australian time).

It was another verbal jab at Wales' rivals in England, a week after they delivered an almost killer blow to the hosts at Twickenham.

Australia play England at Twickenham on Saturday night (Sunday morning AEST) and a win will see the Wallabies and Wales advance through the 'pool of death'.

An England triumph would blow the pool wide open with all three teams fighting for the two places in the next stage of the tournament.

"[If Australia win] it would mean we would make the quarter-finals," Gatland said after a 23-13 win against Fiji.

"It's hard not to be entirely selfish about our own destiny and wanting to make the quarter-finals and Australia can do us a big favour on Saturday."

Gatland is an expert at rubbing salt into England's wounds.

Wales beat England 28-25 last weekend and Gatland took the chance to say he thought England would have settled for a draw in the dying minutes when captain Chris Robshaw turned down a shot at goal to instead go for the win.

The Wallabies will play Wales in the final pool match next weekend and the two teams could be fighting to save their respective campaigns.

The Wallabies have finalised their bench for the clash against England, with coach Michael Cheika opting for Ben McCalman ahead of raging bull Sean McMahon.

McCalman comes into the squad to replace Will Skelton while lock Sam Carter will have to wait for his World Cup debut after being called into the training group this week.

The Wallabies are doing their best to play down any rivalry with England, deflecting questions about the hype and the pressure on the hosts.

Attack coach Stephen Larkham believes the experience of veteran Matt Giteau will help calm the Wallabies' big-game nerves and ease the pressure on playmaker Bernard Foley.

"[Giteau] is a very good communicator and keeps a level head in the back line," Larkham said.

"He adds a bit of spark … guys look to him for communication, he's there to deliver and he's been doing that.

"For Gits … he was a bit concerned about coming into this group and what he could bring, whether he'd be accepted into the group.

"But he's worked really hard on that and the boys look up to him for that experience and knowledge.

Larkham was part of the Wallabies team which was beaten by England in the 2003 World Cup final and knocked out in the quarter finals in 2007.

He said the 2003 match was "the one that got away".

"But I don't think you can draw any reflections on what we're doing this weekend or even this campaign.

"Every game is a big game, it's just whether you get carried away with the hype or not once you get on the field. It's the same contest, it's the same intensity."

Cheika declared "talk is cheap" in the build up to the match after England forward Ben Morgan said the pack wanted to dominated the Wallabies.

WALLABIES TEAM: 15. Israel Folau, 14. Rob Horne, 13. Tevita Kuridrani, 12. Matt Giteau, 11. Adam Ashley-Cooper, 10. Bernard Foley, 9. Will Genia, 8. David Pocock, 7. Michael Hooper, 6. Scott Fardy, 5. Rob Simmons, 4. Kane Douglas, 3. Sekope Kepu, 2. Stephen Moore, 1. Scott Sio. Reserves: 16. Tatafu Polota-Nau, 17. James Slipper, 18. Greg Holmes, 19. Dean Mumm, 20. Ben McCalman, 21. Nick Phipps, 22. Matt Toomua, 23. Kurtley Beale.