Wallaby number eight Wycliff Palu has been ruled out of the remainder of the World Cup due to a hamstring strain.

The 29-year-old limped out of the game against the United States in Wellington last weekend and scans in Christchuch on Monday revealed the extent of the damage, a statement added.

He will require six weeks of rehabilitation before he would be fit to be considered for selection again meaning his World Cup is over.

"It's bad luck for Wycliff. Unfortunately his previous history of injury in this area has impacted, in terms of lengthening the timelines that are required for his rehabilitation," said Robbie Deans.

While Palu will be replaced in Australia's 30-man squad, Deans says the selectors will be taking their time with that decision, and may even delay any call until after this weekend's final Pool match against Russia in Nelson, so they can determine at that point what the team's specific needs are.