Sean McMahon has replaced suspended flanker Michael Hooper in a like-for-like selection for Australia that will ensure the battle at the breakdown will be the key to the Rugby World Cup Pool A decider against Wales.
Australia and Wales have selected two natural opensides in their starting backrow combinations for Sunday's match at Twickenham, upping the tempo in terms of speed and potential for turnovers.
Wallabies coach Michael Cheika picked McMahon to start in the No. 7 jersey for his sixth test, keeping noted fetcher David Pocock at No. 8 and Scott Fardy on the blindside to add some extra height and bulk for the balance of the backrow.
Wales coach Warren Gatland went with a slight variation on the theme, shifting skipper Sam Warburton to the blindside flank to make room for Justin Tipuric on the openside of the scrum, and retaining Taulupe Faletau, a traditional-style No. 8.
The winner will top Pool A and avoid a quarterfinal against two-time champion South Africa. So, even with both teams already qualified for the quarterfinals after their respective wins over England, there's plenty to play for.
"No team ever won the World Cup losing a game," Cheika said. "By winning this game, then you win the group. I don't subscribe to the theory that if you win your group, you are going to get an easier run. That is disrespecting the opposition, and that is not what we are about.
"It is going to be a big game for us. It is going to be a massive battle and pretty painful."
Israel Folau passed a fitness test on his ankle and retained his place at fullback, with veteran Drew Mitchell starting on the wing in place of the injured Rob Horne. In the only other change to the Wallabies' starting lineup that beat England 33-13 last weekend, putting the host team out of the tournament, lock Dean Mumm will start and Rob Simmons moves back to the bench.
Australia has won the last 10 tests against Wales, but the outcomes recently have been decided by less than one try, including the 2014 match at Millennium Stadium where McMahon made his international debut.
Cheika took some convincing initially to go with two natural opensides, forced into the decision purely by the form of both Pocock and Hooper. It worked well in the victory over England, so he resisted shuffling Pocock to openside and bringing in Ben McCalman at No. 8 after Hooper was cited after the Twickenham match for an illegal shoulder charge, and later banned for one match.
McMahon has been the player of the match in his last two tests, including the 65-3 win over Uruguay in Australia's second match at the World Cup.


