Sportal.co.nz 17.Aug.2012Getty Images
Smith is recovering from a detached retina and is expected to be back for the third Test of the Investec Rugby Championship against Argentina.
He has trained with the All Blacks in Auckland ahead of Saturday night's game but Nonu is feeling some pressure filling the role of his mate who has established himself as one of the best centres in the world.
"Obviously I've got big shoes to fill with Conrad having held that jersey for a long time and hopefully I can do him proud," he said.
Smith had been helping out during the week and was in touch again with some aspects of defence he thought he hadn't mentioned but Nonu was happy with where he was at in the build-up to the game.
"I was always on his case, he's so wise in decision-making really and he's pretty much the best 13 [centre] defensively in the world I think," he said.
And having to fill those shoes against Australia, a side which beat New Zealand last year in Brisbane and who provided a real challenge in the World Cup semi-final in Auckland, was going to be tough.
"It's over there in Sydney and they'll be wanting to have a big one," he said.
Nonu said there was a significant adjustment to be made between the second five-eighths and centre positions.
The lines were different. It wasn't possible to stay inside whoever was inside you and there was also countering the Australian approach where wing Digby Ioane had something of a moving brief with fullback Kurtley Beale offering another challenge.
"You can't get caught out," Nonu said.
Quite possibly the biggest challenge he faced was not missing any tackles because missed tackles were rare with Smith was around.
"We've got a few systems in place but you have just got to try and control the outsides," he said.
And while the threat of Quade Cooper had been removed through his non-selection, the danger was under-estimating those who were left. (Halfback) Will Genia and Ioane were just two who were quite capable of stepping up, he said.
"Everyone will be talking about the Australian backline being new and fresh and not attacking, but if we put ourselves in their shoes they'll be playing at home with their backs against the wall and that is where someone is dangerous, so we have to watch out," he said.