Michael Cheika admits it has been a tough call to dump Scott Fardy but says the decision is another sign of a Wallabies team in flux.
Cheika has made two changes to his side for Saturday's crucial Rugby Championship Test against South Africa at Suncorp Stadium as he seeks to snap a horrid six-game losing streak.
Veteran Dean Mumm and highly rated utility Reece Hodge are in, while Lopeti Timani is in contention to become Australia's eighth debutant this year.
But the biggest shock was the axing of back-row stalwart Fardy, sacrificed to make way for Mumm to settle the team's malfunctioning lineout.
"He's been a stable member of the team for a long time now," Cheika told reporters on Thursday.
"Maybe a game off will give him the chance to freshen up and get himself fired up to come back.
"We need, and we are, creating competition in our team. That's what we have to do. As you can see, our team's changing.
"At the end of the day, that competition for places is the best driver for performance."
Mumm, 32, came off the bench in the two Bledisloe Cup defeats to New Zealand but won seven lineouts - more than double the amount of any Australian player so far in the Rugby Championship.
While Cheika said he possessed other good qualities, none was more important this week than his command of the lineout, with Springbok giants Lood de Jager and Eten Eztebeth looming large.
Mumm said there had been a huge focus at training on fixing the lineout.
"It's obviously an area where we can improve significantly. I feel like we're certainly going in the right direction on that," he said.
Hodge, who edged out Drew Mitchell to replace Adam Ashley-Cooper for his first Test start on the wing, caught the eye on debut two weeks ago in Wellington with a monster 55-metre penalty goal.
Cheika plans on using his powerful boot from long range at times, should the opportunity present itself.
"He gives a bit more versatility around how we want to set the team up attacking and defensively," he said.
The rest of the side remains untouched, with Cheika continuing to resist calls to move Israel Folau to the centres or dump the hotly debated Michael Hooper-David Pocock combination.
Timani and Sean McMahon are the new faces on a nine-man bench, which will be trimmed on Friday by one.
Wallabies: Israel Folau, Dane Haylett-Petty, Samu Kerevi, Bernard Foley, Reece Hodge, Quade Cooper, Will Genia, David Pocock, Michael Hooper, Dean Mumm, Adam Coleman, Kane Douglas, Sekope Kepu, Stephen Moore (capt), Scott Sio. Res: Tatafu Polota-Nau, James Slipper, Allan Alaalatoa, Rory Arnold, Lopeti Timani, Sean McMahon, Tevita Kuridrani, Drew Mitchell (one to be omitted).
