Wallabies No.8 Toutai Kefu is out for four weeks with a shoulder injury, continuing a frustrating run of injuries for Australia's leading forward.

Kefu has been diagnosed with a fractured shoulder blade, suffered in Australia's 21-17 Bledisloe Cup loss to New Zealand last Saturday.

He was forced off Eden Park 10 minutes into the second half, after a bone-crunching tackle by his All Blacks opposite Jerry Collins.

While Wallabies officials put on a brave face, saying their key ball-runner was in no doubt for Australia's opening World Cup clash with Argentina on October 10, the injury was a serious setback to Kefu's preparation.

It continued a disappointing run of injuries for the Australian vice-captain.

He suffered a spinal injury in a late hit by Springboks prop Robbie Kempson during their Tri-Nations last month, and then a calf strain at training hampered his build-up for the Auckland match.

"I've got six weeks until I'm fully back playing but I'm governed by how it feels from here on in," said Kefu, while nursing his baby daughter Madison, who was born just after full-time on Saturday.

"If it feels alright after a week or so I can probably start to jog lightly and if it hurts too much I'll have to pull back so I'll just see how it feels over the next few weeks."

He said the injury had come at a frustrating time because he felt he was nearing his best.

"I think physically and mentally I was just peaking at the right game, the Bledisloe," he told Fox Sports

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