Wallabies coach Michael Cheika faces perhaps "the biggest challenge" of his career in Saturday's Rugby Championship clash against New Zealand in Wellington, a week after his side were humiliated by the same opposition in Sydney.

The former Leinster coach earned praise for winning last year's tournament and leading Australia to the 2015 World Cup final just 12 months after taking over a disorganised unit but a 3-0 home series loss to England in June signalled the end of his honeymoon period.

The slump continued when last week's 42-8 mauling by a rampant All Blacks handed Cheika a fourth consecutive home defeat and the 49-year-old offered a frank assessment of the task ahead when asked where it ranked in his coaching career.

"Probably the biggest. It's a big stage and it's a big challenge for us," Cheika told the Australian Associated Press on Tuesday.

"The criticism from the performance (last weekend) is very warranted, no doubt about that, and when there's a lot of that talk in your head you start to get weighed down by it.

"(The players) are feeling pretty terrible about it, so we've got to get them back up into a situation where that's driving them to do something better this weekend."

Cheika dismissed criticism of his selection of veteran backs Will Genia, Matt Giteau and Adam Ashley-Cooper, brought back from France under the "Giteau rule" which he introduced ahead of the World Cup to add vital experience to his squad.

"I thought Will Genia was one of the players who did stand up in that game," Cheika added.

"Since I've been here, win or lose, we've always been pretty true to our identity and that's the first time I don't think that we have, and we've got to make that right.

"It hasn't gone this year how we wanted it to, but we're not going to go and cry with our thumb in our mouth back to mummy.

"We're going to get in there and fight and get ourselves sorted out and that may be enough. It may not be. But that's what we're definitely going to do this weekend."

Cheika will also need to address his options at inside centre following the loss through injuries of Giteau, Matt Toomua and Rob Horne last weekend.