Folau (ankle) and Pocock (calf) must complete training at the team's last session on Saturday (Sunday morning AEDT) to put to bed doubts about their fitness ahead of the clash against Argentina.

But both have been named in Michael Cheika's team while Scott Sio (elbow) has been ruled out, allowing James Slipper to move into the starting XV and become the most capped prop in Australian rugby history.

The Wallabies only just survived a quarter-final scare against Scotland last weekend with Folau and Pocock on the sideline.

Their return is a massive shot in the arm for Australia's hopes ahead of their match at Twickenham on Sunday (Monday morning AEDT), but Ashley-Cooper said they can't shoulder the expectation.

"It's a great boost, it's good having those guys there. They are world-class players, hence the time [coach Michael Cheika] has given them to prove their fitness," Ashley-Cooper said.

"Having those two back is definitely a boost but we can't rely on them coming back in and performing everything. We have to perform our role.

"The squad is healthy and available. That's the boost. We have relied on that depth in a couple of games, we can get a lot of confidence out of that."

Sio will stay with the squad in the hope that he will be fit for the final if Australia can beat Argentina.

His injury has opened the door for Slipper to etch his name in the Wallabies' history books, passing Benn Robinson and Ben Alexander as Australia's most capped front-rower.

It comes a week after Slipper felt "sick in my stomach" after he threw an intercept pass which allowed Scotland to score and almost destroyed the Wallabies' World Cup dreams.

But Cheika is throwing his faith in Slipper to step up at loosehead prop while Sio will be given extra time to recover.

Winger Drew Mitchell has a chance to snatch a record of his own as he edges closer to the top of the World Cup try-scoring list.

Mitchell is just one behind New Zealand legend Jonah Lomu and South Africa speedster Bryan Habana.

But he is more focused on making the most of his opportunity to claim team glory.

"Regardless of whether it was Izzy or [Kurtley Beale] or Ben McCalman or Poey, we've got the belief in the group that we've got the cattle to go out there and get the job done," Mitchell said.

"This week [Pocock and Folau] along with 21 other players are getting opportunities to pull on the jersey, go out there and make the most of what is a great opportunity for us."

WALLABIES TEAM: 15. Israel Folau, 14. Adam Ashley-Cooper, 13. Tevita Kuridrani, 12. Matt Giteau, 11. Drew Mitchell, 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. James Slipper. Reserves: 16. Tatafu Polota-Nau, 17. Toby Smith, 18. Greg Holmes, 19. Dean Mumm, 20. Ben McCalman, 21. Nick Phipps, 22. Matt Toomua, 23. Kurtley Beale.