The Wallabies have suffered a a late blow ahead of their important clash with Ireland in Auckland with the news that breakdown ace David Pocock will not be able to play.

Pocock was withdrawn from the team due to soreness associated with a back strain and his absence sees his Western Force teammate, Ben McCalman, promoted into the starting XV to play his 15th Test, but his first as an openside flank.

The promotion of the 23-year-old loose forward also paves the way for Waratahs No. 8 Wycliff Palu to be included on the bench, with Australian coach Robbie Deans opting to retain a five-forward, two-back split on the replacements bench.

Should Palu enter the game, it would be his 37th Test appearance, but his first since Australia beat Wales 33-12 at the end of its 2009 year-end tour of Europe.

Palu missed all of last year's international season, and this year's Tri Nations, due to injury.

Pocock trained fully on Thursday but missed Friday's captain's run after waking up with soreness in his lower back. It is an issue that has troubled the star loose forward before. He reported less discomfort this morning but the improvement wasn't enough to determine a readiness for him to play.

While Saturday's match promises to be critical in determining the winner of Pool C, Deans said he was not prepared to take any risks with Pocock.

He explained: "It's more of an on-going irritation than anything serious, scans have shown nothing sinister, but David is a key member of our group. We would rather give him a bit of time to get it right before putting him back out there.

"Although Ben [McCalman] isn't a recognised openside, he does have some recent background there and has trained in the role on a regular basis with us this year. We were looking to give him an outing on the openside before our Pool programme concluded, it's now just come a bit earlier than we'd originally planned..

"He is well suited to the role, being strong around the contact area and good over the ball, which is a legacy of his time in the Australian Sevens programme. He's looking forward to the opportunity and we believe in him. That's why we opted to utilise him as David's back up when we looked at our selection mix for the squad."

McCalman has previously appeared at No.8 and blindside in Test matches but has showcased his versatility in Super Rugby by also featuring at lock.

Australia are chasing their first win at Eden Park since 1986, albeit not against New Zealand, while Ireland has never won at the famous ground.

Revised Australia team: 15 Kurtley Beale, 14 James O'Connor, 13 Anthony Fainga'a, 12 Pat McCabe, 11 Adam Ashley-Cooper, 10 Quade Cooper, 9 Will Genia, 8 Radike Samo, 7 Ben McCalman, 6 Rocky Elsom, 5 James Horwill, 4 Dan Vickerman, 3 Ben Alexander, 2 Stephen Moore, 1 Sekope Kepu               
Replacements: 16 Tatafu Polota Nau, 17 James Slipper, 18 Rob Simmons, 19 Wycliff Palu, 20 Scott Higginbotham, 21 Luke Burgess, 22 Drew Mitchell.            

Date: Saturday, September 17
Venue: Eden Park, Auckland
Kick-off: 20.30 (08.30 GMT)
Referee: Bryce Lawrence (New Zealand)
Assistant referees: Dave Pearson (England), Stuart Terheege (England)
TMO: Graham Hughes (England)