The Wallabies are putting faith in their back-line depth to rise to the challenge against Wales as they brace for combination changes.
The Wallabies face their biggest stumbling block of the World Cup when they face Wales at Twickenham on Saturday night (Sunday morning AEDT). 
Vice-captain Michael Hooper is suspended, while the back line has hit an injury hurdle with Israel Folau (ankle), Rob Horne (shoulder) and Giteau (ribs) all fighting to be fit for the clash.
The Wallabies and Wales have confirmed their place in the quarter-finals. But the winner of the pool of death decider will get a smoother path through the play-offs and avoid New Zealand and South Africa until the final.
Giteau was left writhing in pain after England playmaker Owen Farrell hit him without the ball in the Wallabies' 33-13 win last weekend.
ACT Brumbies pivot Matt Toomua looms as the most likely candidate to fill Giteau's shoes if the 98-Test veteran is unable to take his place at inside centre against Wales.
Giteau has been in superb form, coinciding with the ARU changing its eligibility rules to allow overseas-based players to be selected for the Wallabies.
He has formed a strong midfield combination with Bernard Foley, who scored 28 points against England, but veteran star Adam Ashley-Cooper was confident the Wallabies had the depth to cover any back-line absences.
"It is something we really haven't had in a long time," Ashley-Cooper said. "We are going to be tested this weekend. There are question marks around Izzy and his ankle, Rob Horne and his shoulder, Gits didn't train this morning because of his ribs, I am sure he'll be right."
Kurtley Beale and Drew Mitchell are the likely replacements for Folau and Horne. But coach Michael Cheika will give each player a chance to prove their full fitness.
Horne showed his courage when he jumped into the Wallabies' defensive line against England, despite a partial dislocated shoulder.