Head coach Robbie Deans played down the seriousness of the injury but admitted that he could not risk Pocock doing more damage to his back against pool rivals Ireland.
"It's more of an ongoing 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," he said.
Pocock's Western Force colleague Ben McCalman has been selected to replace him in the starting back row. It will be his first Test outing at openside, with all ten of his previous starts coming at number 8.
"We were looking to give Ben an outing on the openside before our pool programme concluded. It's now just come a bit earlier than we'd originally planned," added Deans.
"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."
The injury to Pocock also opens the way for Wycliff Palu to earn a recall to the replacements bench. The hard-hitting Waratahs back rower has been troubled by injuries in recent seasons - his last appearance for the Wallabies was against Wales back in November 2009.
AUSTRALIA Team & Replacements (v Ireland, 2011 Rugby World Cup Pool C, Eden Park, Saturday, September 17, kick-off 8.30pm local time/9.30am Irish time):
15 - Kurtley Beale (NSW Waratahs)
14 - James O'Connor (Western Force)
13 - Anthony Fainga'a (Queensland Reds)
12 - Pat McCabe (Brumbies)
11 - Adam Ashley-Cooper (Brumbies)
9 - Will Genia (Queensland Reds)
1 - Sekope Kepu (NSW Waratahs)
2 - Stephen Moore (Brumbies)
3 - Ben Alexander (Brumbies)
4 - Dan Vickerman (NSW Waratahs)
5 - James Horwill (Queensland Reds) (capt)
6 - Rocky Elsom (Brumbies)
7 - Ben McCalman (Western Force)
8 - Radike Samo (Queensland Reds)
16 - Tatafu Polota Nau (NSW Waratahs)
17 - James Slipper (Queensland Reds)
18 - Rob Simmons (Queensland Reds)
19 - Wycliff Palu (NSW Waratahs)
20 - Scott Higginbotham (Queensland Reds)
21 - Luke Burgess (NSW Waratahs)
22 - Drew Mitchell (NSW Waratahs)
Follow the Ireland team in New Zealand on www.twitter.com/irfurugby.