Wales v Australia
Fly-half Stephen Larkham hurt his knee during Australia training
Millennium Stadium, Cardiff
Saturday, 15 September
Kick-off: 1400 BST
Live coverage on BBC Radio 5live, Radio Wales, Radio Cymru & the BBC Sport website
Australia fly-half Stephen Larkham has been ruled out of Saturday's Pool B showdown with Wales with a knee injury.
The 33-year-old, who has won 102 caps, twisted his knee in kicking training on Friday and has failed to recover in time for the Millennium Stadium clash.
Larkham is to undergo exploratory surgery on Monday and will also miss next Friday's match against Fiji.
Berrick Barnes, who made his Test debut in last Saturday's win over Japan, will take the number 10 shirt in Cardiff.
Wallabies coach John Connolly said he hoped Larkham would return for Australia's last pool match on 29 September against Canada in Bordeaux.
Australia had already brought Drew Mitchell and Guy Shepherdson into their side from last weekend.
Prop Shepherdson replaces Al Baxter, Mitchell taking Adam Ashley-Cooper's place on the wing.
Baxter is joined on the bench by Julian Huxley, who is in after Ashley-Cooper's toe injury ruled him out on Friday.
Connolly has kept experienced back-rower Phil Waugh on the bench, with George Smith starting.
The selection has a strong and experienced look, with lock Dan Vickerman winning his 50th cap.
Connolly has reverted to a 5-2 split on his reserves bench, selecting five reserve forwards and two replacement backs.
Flanker Waugh is the major beneficiary of the move, named as a replacement after missing out on selection against Japan.
Playing in front of a packed Millennium Stadium in a World Cup will be an unforgettable experience for the players
Australia coach John Connolly
Mark Chisholm is in line to make his World Cup debut after claiming the reserve lock's spot, while utility back Scott Staniforth is also on the bench.
Wing Mark Gerrard was ruled out of the World Cup after rupturing a knee in Saturday's opening 91-3 win over Japan in Lyon, utility back Cameron Shepherd called into the squad in his place.
"This is a crucial game as far as our pool is concerned and a lot of what we have done over the past 12 months has been preparing us for this game," said Connolly.
"Playing in front of a packed Millennium Stadium in a World Cup will be an unforgettable experience for the players, it's something they will treasure for the rest of their lives."
The winner of the match is likely to finish top of Pool B and play the second-placed team in Pool A, headed by South Africa and holders England, in the quarter-finals.
Australia: Chris Latham; Drew Mitchell, Stirling Mortlock (capt), Matt Giteau, Lote Tuqiri; Berrick Barnes, George Gregan; Matt Dunning, Stephen Moore, Guy Shepherdson, Nathan Sharpe, Dan Vickerman, Rocky Elsom, George Smith, Wycliff Palu.
Replacements: Adam Freier, Al Baxter, Mark Chisholm, Stephen Hoiles, Phil Waugh, Scott Staniforth, Julian Huxley.