Sean McMahon will substitute the one match banned Michael Hooper as openside flanker, Exeter’s Dean Mumm takes Rob Simmons’ place in the second row and Drew Mitchell comes joins the left wing to replace the shoulder injured Rob Horne.
The unleash of Wallabies Sean McMahon means Australia will continue to deploy two openside flankers in the back-row.
Wales have also gone with two opensides in their back row with Sam Warburton and Justin Tipuric.
“Every match in this tournament has required our team to step up to another level and we’ll need to do that again against an undefeated Welsh team,” said Michael Cheika.
“Every player in our squad knows the improvements required, and we still have two days to continue to make them, both individually and as a team.
“Saturday night at Twickenham is another opportunity for us to put in a solid performance and continue to build towards the next stage of the tournament.”