Cheika has rotated his troops through the pool phase, not endearing himself to those who believe a rock-solid XV should have been already established heading into Saturday's quarter-final in Oita.

Instead there are question marks, something the coach has encouraged, believing he has the player depth to create a sense of competition.

Cheika's 68th, and possibly final, Australian team announcement on Thursday will finalise who he rates as his premier outside back combination, along with his desired loose forward mix.

The identity of his first choice five-eighth has also been uncertain in Japan, having changed in every game.

However, Cheika's comments on Monday that he has deliberately rested Christian Lealiifano to keep him physically sharp suggests the Brumbies veteran will wear No.10.

Out wide, Reece Hodge's return from suspension gives Cheika access to a player he's trusted on the right wing all year.

But there are options galore there, including the in-form Dane Haylett-Petty, rookie Jordan Petaia and veteran Adam Ashley-Cooper.

Haylett-Petty could well be the fullback, given Kurtley Beale's patchy form and reduced training minutes this week while he recovers from a head knock.

The big stage may not prevent Cheika from taking a punt on 19-year-old Petaia, who was quiet against Georgia last week but showed enormous promise on debut against Uruguay a week earlier.

Hodge himself conceded nothing was guaranteed and that Petaia had all the weapons to be a Test star.

"He's a pretty special player so to see him score a try on debut and have some pretty special touches was pretty cool," Hodge said.

"We all knew it was going to happen at some point.

"But obviously Swoop (Ashley-Cooper) put in a couple of really good performances against Wales and Uruguay.

"Dane's a consistent performer as well and KB's had some special touches.

"We'll need to see. No spot is ever guaranteed in the team."

Flanker David Pocock unleashed his best display of the tournament against Georgia and is favoured to remain when captain Michael Hooper returns from a week off.

That would leave Cheika to pick between Isi Naisarani, Jack Dempsey and Lukhan Salakaia-Loto in a more muscular back row role.

"They do things a little bit differently, the three other guys," Cheika said this week.

"They've all got their different skill-sets. So it's about trying to taylor-make what we think will work for us. We believe we have a good plan about how we're going to go about the game, a strong plan, and whichever player fits into the plan the best will get the nod."

Naisarani had the worst game of his rookie season against Georgia, including a yellow card, but consistent runs on board through 2019 may swing selection in his favour.

POSSIBLE WALLABIES XV

Dane Haylett-Petty, Jordan Petaia, James O'Connor, Samu Kerevi, Marika Koroibete, Christian Lealiifano, Nic White, Isi Naisarani, Michael Hooper (capt), David Pocock, Rory Arnold, Izack Rodda, Allan Alaalatoa, Tolu Latu, Scott Sio.

Australian Associated Press