The All Blacks returned to New Zealand after another Rugby Championship demolition of Australia but with concerns over the long-term health of Ryan Crotty.
The inside centre was knocked out in a clash of heads with midfield partner Jack Goodhue in the first half of the 38-13 rout at Sydney's Olympic stadium and played no further part in the match.
Crotty, 29, has suffered a litany of head knocks over the past two seasons, missing games for the Canterbury Crusaders in Super Rugby earlier this year, and will be sidelined for Saturday's return match at Eden Park.
All Blacks coach Steve Hansen lamented Crotty's "bad luck" and said a specialist had already given the midfielder the "all-clear".
Flanker Sam Cane, however, was circumspect about the "fickle" nature of head injuries.
"Everything else has a timeframe but there's just so much unknown with head knocks and it seems like you can be only one away, if it's the wrong one, from it being then end of it," Cane told reporters in Sydney on Sunday.
With Sonny Bill Williams already ruled out with injury, the All Blacks will have to dig deep into their midfield stocks.
Anton Lienert-Brown, who replaced Crotty on Saturday, or Ngani Laumape are likely to start at inside centre, with the uncapped Vince Aso a chance to be called up as injury cover.
The All Blacks will also be without winger Rieko Ioane, who suffered a hamstring strain, which opens the door for a recall to Nehe Milner-Skudder.
The All Blacks can win the Bledisloe Cup, the annual trophy contested between the trans-Tasman nations, for a 16th successive year with victory at Eden Park, where they have not lost to Australia in 32 years.
Hansen, however, said they had to be wary of a wounded Wallabies side.
"Their backs are against the wall and they're going to improve," he said. "What we do know is that teams that get beaten learn more than teams that win, and teams that get beaten are hungrier than teams that win.
"Our challenge this week is to learn better and be hungrier than them."
