Umaga remains upbeat over a return

The All Blacks vice-captain ruptured his cruciate knee ligaments during their opening pool victory over Italy when he collided with Carlos Spencer.

"At this stage we are looking to see if he will be available at quarter-final time," said Mitchell.

"He is on track for that but there are no guarantees."

Mitchell added: "He is jogging and cycling and swimming. This week is essential for him in rehab."

I seem to be improving every day Tana Umaga

Such is the growing confidence among the All Black management, Norm Maxwell, who has been training in Australia in preparation to join the squad, has been sent home.

He will return to New Zealand with Ben Blair, who injured his neck in a training accident.

Umaga is determined to stay in Australia for the remaining three weeks before the quarter-finals and prove his fitness.

"If I didn't have that goal I'd probably be at home by now," said the 30-year-old. "I want to play in this tournament.

"I have worked hard to get to the World Cup and I want to be successful. That is what I am aiming for.

"The coaches have shown faith in me so that has given me confidence to keep working hard."

Williams returns for All Blacks

Mitchell's other injury concern is utility back Aaron Mauger who has bruised a bone in his knee.

"It is not a serious injury, it's a bone bruise," Mitchell added.

"He had pain walking but that has gone now."

New Zealand meet Tonga in their next game on 24 September in Brisbane.