Australia crushed Russia 68-22 to reach the World Cup quarterfinals on Saturday but the victory was overshadowed by a hamstring injury to winger Drew Mitchell that appears likely to have ended his tournament.
The Wallabies join New Zealand and South Africa in the last eight and they might have to beat both their Tri-Nations rivals to reach the final if Ireland beat Italy on Sunday to finish top of Pool C.
Two-times champions Australia, who have only once before failed to qualify top of their pool, lead the group with 15 points ahead of Ireland, 13 and Italy on 10 ahead of their Dunedin showdown.
A quarterfinal against the Springboks looks likely but they could still win the pool to play either Wales or Fiji.
Australia's bonus-point victory was always going to be a formality but, having been forced to start with loose forward Radike Samo on the wing, Mitchell's hamstring problem is the last thing the Tri-Nations champions would have wanted.
They will be pleased with the sharpness shown in the first half as Berrick Barnes and Quade Cooper cut holes in some admittedly feeble defence to send their runners away while James O'Connor converted nine of the 10 tries.
After turning round 47-5 ahead, Australia lost momentum, and as rain made conditions difficult, Russia fought back with spirit to end their World Cup debut on a positive note.
"Overall, we're happy to get the win but at the back end there things didn't really go the way we wanted," Australia captain James Horwill told reporters.
"We did what we needed to do and now we move on and just wait to see who we play next week."
The Wallabies hit the ground running and scored some lovely tries during 40 minutes of virtual one-way traffic.
Impressive flanker David Pocock scored two while hooker Stephen Moore finished off a cracker after a wonderfully visionary pass by Mitchell.
Mitchell added his second try after the break but then pulled up when going for what would have been his third and coach Robbie Deans said later that the injury "looks a bad one" for the winger, who suffered a horrific broken leg in April.
"It doesn't look good. It looks like it will end his tournament," Deans lamented.
"Drew is bitterly disappointed, the whole team is disappointed for him," Horwill added.
Barnes, who had a lively game starting at inside centre, ensured Australia finished on top when he intercepted to score his second try in the final minutes.
That was hard on Russia, who could barely make a tackle in the first half but were a different side after the break.
They dominated for long spells, played some creative rugby and ended the day with three tries by Vladamir Ostroushko, Denis Simplikevich and Konstantin Rachkova.
"It was amazing, we didn't get the best of starts and we struggled to keep our composure initially," Russia fullback Vasily Artemyev said.
"In the second half we had nothing to lose so we really tried to hold onto the ball and use our backs and score a few tries.
"We put a few things right and I think we deserved our tries."
Australia - Tries: Berrick Barnes (2), Drew Mitchell (2), Ben McCalman, David Pocock (2), Stephen Moore, Adam Ashley-Cooper, Salesi Ma'afu. Conversions: James O'Connor (9)
Russia - Tries: Vladimir Ostroushko, Denis Simplikevich, Konstantin Rachkov. Conversions: Rachkov (2). Drop Goal: Rachkov.