Crotty head injury sours All Blacks' triumph

Concerns over the long-term health of Ryan Crotty are back in the spotlight after he suffered another concussion during the All Blacks win over the Wallabies.

The inside centre was knocked out in a clash of heads with new 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.

The 29-year-old 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.

His sister Shea Crotty, who has played basketball for New Zealand, aired her concerns on social media.

"Know how frustrated he will be but for selfish reasons I want to see my brother grow old and able, not battling the brain forever," she wrote on Twitter.

All Blacks coach Steve Hansen lamented Crotty's "bad luck" to be hit by friendly fire 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.

Injuries aside, Hansen would have been immensely pleased with the performance of the champions, who notched their 13th successive win in the tournament after going undefeated in the last two campaigns.

Captain Kieran Read made a solid return to the side after a long lay-off from back surgery while lock Brodie Retallick was brilliant in his first test for nearly a year, scoring a second half try and adding huge drive to the All Blacks' scrum.

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."