Kalyn Ponga is expected to miss the rest of the World Cup after sustaining a suspected fractured arm during Australia's opening match.
Mitchell Moses' tournament is also in doubt after a calf injury forced him off early in Australia's 24-22 win over New Zealand.
Scans will determine the injury's extent, and coach Kevin Walters acknowledged it could end Moses' campaign.
Walters confirmed Sam Walker, left out of the opener, will play against Fiji in Brisbane on Saturday week.
"He'll (Walker) play next week. We'll put him alongside Tom who will play five eighth," Walters said.
Walters indicated Cameron Munster would rest, while Tom Dearden would partner Walker in the halves.
Canberra playmaker Ethan Strange, named among Australia's shadow players, could replace Moses if he is ruled out.
"We can bring Ethan in if Mitch is ruled out for the tournament so we'll see how that goes in the next couple of days," Walters said.
Walters is expected to retain James Tedesco at fullback instead of Reece Walsh, despite Walsh's long-range try in the comeback victory.
Bradman Best is in contention to replace Kotoni Staggs, whose performance prompted calls for his omission.
Staggs dropped a try, was beaten by Ponga and was sin-binned for a professional foul near Australia's line.
New Zealand scored a penalty and a try while Staggs was off the field.