AUSTRALIA head coach Michael Cheika has made three changes to his side to face Wales at Twickenham in Saturday's Rugby World Cup Pool A showdown (kick-off 4.45pm).

Wallabies rookie of the year Sean McMahon will replace Michael Hooper in one of three changes to the starting line-up that faced England.

The Wallabies have been forced into two changes with Rob Horne (shoulder) and Hooper (suspension) ruled out for the match which will determine the winner of Pool A.

McMahon slots straight in at number seven with David Pocock remaining at number eight to make his fourth start at the back of the scrum. Pocock will also share the vice-captaincy with Adam Ashley-Cooper.

Veteran Drew Mitchell comes onto the wing for Horne, after a two-try performance against Uruguay earlier in the tournament made him the third-highest try scorer in Rugby World Cup history.

Dean Mumm has also been included for the second time at Rugby World Cup 2015, pairing up with Kane Douglas at lock with Rob Simmons moving to the bench.

Fullback Israel Folau has overcome an ankle injury to take his place in the side, continuing his good run with the Wallabies having not missed a Test through injury since his 2013 debut against the British & Irish Lions.

Scott Sio is the only player to start in every Test for the Wallabies so far in the tournament, remaining at loosehead prop for the pivotal match.

Cheika said the team's focus remains firmly on the task at hand.

"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.

"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."

Australia starting XV: 1. Scott Sio (13 Tests) 2. Stephen Moore - c (98 Tests) 3. Sekope Kepu (59 Tests) 4. Kane Douglas (19 Tests) 5. Dean Mumm (40 Tests) 6. Scott Fardy (26 Tests) 7. Sean McMahon (5 Tests) 8. David Pocock - vc (52 Tests) 9. Will Genia (62 Tests) 10. Bernard Foley (23 Tests) 11. Drew Mitchell (66 Tests) 12. Matt Giteau (98 Tests) 13. Tevita Kuridrani (27 Tests) 14. Adam Ashley-Cooper - vc (110 Tests) 15. Israel Folau (35 Tests).


Replacements: 16. Tatafu Polota-Nau (57 Tests) 17. James Slipper (70 Tests) 18. Greg Holmes (20 Tests) 19. Rob Simmons (56 Tests) 20. Ben McCalman (43 Tests) 21. Nick Phipps (35 Tests) 22. Matt Toomua (28 Tests) 23. Kurtley Beale (56 Tests)