Ryan Jones has withdrawn from the Wales side to take on Australia in the Invesco Perpetual Series climax at the Millennium Stadium on Saturday (Kick-off 5.30pm).
Gethin Jenkins will captain the team and Jones is replaced at No8 by Andy Powell, who moves across the back row, with Dragons flanker Dan Lydiate promoted from the bench to the blindside to win his second cap.
Lydiate's place as a replacement is taken up by Sam Warburton, who faces the prospect of tackling the Wallabies for the second time in a week after representing the Cardiff Blues against their midweek touring side on Tuesday.
"Ryan pulled up in Tuesday's conditioning session with a back problem," said Wales physio Mark Davies.
"This obviously needed time to settle and unfortunately the problem has not resolved in time for him to be available on Saturday.
"He has been receiving treatment and was unable to train yesterday, but today we have taken the decision that he is simply not going to be ready to take the field."
Sam WARBURTON (CARDIFF BLUES - Cap No 1,070)
DoB: 05.10.88. 1.88m / 6'2". 15st 9lbs / 99kgs
International record: 2 caps (W 2)
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We caught up with Shona and Ellie from the Wales women team ahead of the start of the Women's Rugby World Cup in Paris next month at a recent women's training session to encourage and promote more women and girls to try their hand at rugby. #tryourgame
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Wales completed their Junior World Championship campaign with a victory over Samoa. Team manager Mark Taylor and No 8 James Benjamin reflect on a tournament which saw Wales win three games and lose two.