Tokyo - Wallabies vice-captain Berrick Barnes injured his left ankle in training on Thursday and was ruled out of the Bledisloe Cup Test against the All Blacks on Saturday.
The 23-year-old inside centre could also be in doubt for Australia's Grand Slam tour of Britain and Ireland, their first in 25 years, following the year's fourth and final trans-Tasman Test.
His withdrawal prompted Wallabies coach Robbie Deans to change the team, bringing teenager James O'Connor from the bench to fullback and moving Adam Ashley-Cooper from fullback into Barnes's position.
Barnes, his left foot taped, was seen limping out the training ground on crutches on his way to a hospital for scans.
"He rolled his ankle so he won't be playing this weekend," Wallabies media manager Matt McIlraith said, adding that the full extent of the injury may be known in the "next day or so".
"As far as Berrick's situation concerning the rest of the tour, we still don't know."
Barnes' teammates said they were disappointed but still confident they could wage a full-out battle to end their six-Test losing streak against New Zealand.
The Wallabies have been without a try for 236 minutes since Barnes crossed the line in the fourth minute of their first Test against the All Blacks in Auckland in July.
"It is unfortunate for him and for us to lose a player on Thursday," said lock James Horwill. "But we are moving forward. We are still confident that the guys in there are going to be more than able to do their jobs."
Ryan Cross, who was slotted in at outside centre, said his side would now have two running centres.
"Obviously we'll have to change our style a bit," he said. "I think we will play the best we can."