There has been an upward curve in momentum and performance from the Wallabies to emerge unbeaten in Pool A while other quarter-finalists' form graphs have wavered.
The impact from the Wallaby scrum has been a massive statement and the squad's fitness is top grade. They've had to soak up plenty of punishment and several of their senior men are battling repeat injuries.
Can they afford to rest David Pocock (leg), Israel Folau (ankle) and Matt Giteau (ribs) against Scotland and trust the depth in the squad, will they be forced in those decisions or will they roll the dice once more with their wounded warriors?
Those are some of the decisions Cheika faces as he assesses the casualties in his group and the task against Scotland.
He will get refreshed flanker Michael Hooper back from his week's ban and could also use young Sean McMahon who put in a very strong shift against Wales.
Folau is struggling with his ankle problem although he still managed several dangerous bursts against Wales. He was less dominant than usual in the air and made fewer running forays which pointed to his troubles.
Whether an extra week's rest will help Folau is something the Wallaby medical staff will weigh up while there is a risk the Wallabies may not survive for the semis.
Sore ribs have troubled Giteau for several weeks and it's a matter of whether he can play through the discomfort or is too inconvenienced and the side would benefit from a fully fit sub like Matt Toomua.
Giteau's left foot has been a valuable balance to help Bernard Foley and his experience has helped guide the midfield defensive line through several tight tussles. The Wallabies have yielded just two tries in four matches and coupled with the growing consistency of their scrum, that is making them a very awkward opponent.
