All Blacks coach Steve Hansen has warned the budding midfield combination between Sonny Bill Williams and Ma'a Nonu will only continue to grow after New Zealand gave the physically imposing duo a pass mark for their efforts against Australia.

Saturday's Rugby Championship game in Sydney represented only the third time the two have combined in the centres and it was just the second occasion with Williams at inside and Nonu at outside.

Much of their pre-match talk centred on the attacking qualities of the two 100kg-plus midfielders.

However they were solid in defence and were used to devastating effect as decoy runners in the build-up to both of New Zealand's tries in Saturday's 27-19 win.

Hansen praised Nonu for his defence and the part played in his improvement in that area by New Zealand's premier No.13, Conrad Smith, who is currently injured.

"I think he (Nonu) has matured a lot defensively, he's not that gung-ho rushing player he was when he was younger," Hansen said.

"Conrad (Smith) needs to be complimented. He did a lot of work with him this week making sure they spent time together and I thought defensively tonight he was outstanding.

"The combination with Sonny will grow from having this 80 minutes tonight, so happy enough with the both of them."

A last minute penalty denied Australia a bonus point and Hansen took satisfaction from that and the feeling the world champions had scope for improvement.

"Really pleased that we were able to get that win away from home and even more pleased to make sure they didn't get a point as far as the Championship goes," Hansen said.

"I thought we had some really good displays from our guys."

Captain and openside flanker Richie McCaw refused to get too excited about the potential for securing the Bledisloe Cup for a tenth straight year.

"I think history has shown when we've played back to back Tests that if you don't get your prep right you can trip up," McCaw said.

"That's our challenge is to get past this game and work out ways we can turn up and play better.

"There's no doubt the Wallabies will do that and both teams will be better."