All Blacks centre Sonny Bill Williams could miss Saturday's Bledisloe Cup decider in Auckland after sustaining an injury against Australia in Sydney.
New Zealand's coach Steve Hansen said Williams injured his tailbone after a heavy fall midway into the first half of the Rugby Championship clash which Australia won 27-19.
He is unlikely to train on Tuesday but has not been ruled out of the upcoming Test at Eden Park.
"He landed on his rear end… got a knock on the buttock and that's tightened up so we'll have to see how he goes," explained Hansen.
Williams looked out of sorts for most of the match and his injury could explain his hesitation to take the ball in to contact against the Wallabies and he was eventually replaced by Malakai Fekitoa in the 55th minute.
His potential absence in Auckland could be offset by the return of Ma'a Nonu, who has recovered from a shoulder injury sustained in the All Blacks' win over the Springboks in Johannesburg last month.
"Ma'a's fine and Sonny could still come right," added Hansen.
"We'll just wait until we get through to Tuesday and make some assessments then."
Meanwhile, Hansen had good news on Ben Smith who was knocked out after trying unsuccessfully to prevent Adam Ashley-Cooper from scoring a try in Sydney.
"Ben is good," he said.
"Even after the game he was tested and got 30 out of 30 in his [concussion] test and this morning he's not suffering from anything,"
"We'll do what we always do, we'll do all the tests and we won't play him if he's not right."