Sean McMahon will replace Michael Hooper in Australia’s side to take on Wales at Twickenham on Saturday in one of three changes to the Wallabies’ starting line-up that faced England. The Wallabies have been forced into two changes with Rob Horne (shoulder) and Michael Hooper (suspension) ruled out for the match which will determine the winner of Pool A. McMahon slots straight into the seven jumper, the 21-year-old's second run-on selection for the tournament, 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. 66-Test 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 in the Wallabies run-on team for the second time at Rugby World Cup 2015, pairing up with Kane Douglas at lock with Rob Simmons moving t