Their brazen confidence follows Australia stunning the world champions 47-26 in Perth last weekend, although the New Zealanders were a man down for the entire second half after lock Scott Barrett was sent off.
FitzSimons, now a media commentator, said the Wallabies "simply outclassed the All Blacks" in the record win.
"They humiliated those poor All Blacks and it was good for rugby," he said on Newstalk ZB radio.
The scale of the defeat raised questions about whether New Zealand's dominance was at an end, and about the wisdom of relying on players aged over 30.
"Sonny Bill Williams is 34, how's Sonny Bill going to go up against James O'Connor?" FitzSimons said. "The All Blacks just looked a bit old and slow."
Earlier this week, the Sydney Daily Telegraph poked fun at the "Old Blacks" by manipulating photos of Williams, skipper Kieran Read (33) and Sam Whitelock (30) to make them look like elderly men.
Williams responded by saying he had faith in the senior players to win the match in Auckland and retain the annual Bledisloe Cup, which Australia have not won since 2002.
"Australia are coming, we know that, but we're hungry to keep that Bledisloe as well - so don't forget that," he said.
In response to the Perth defeat, New Zealand coach Steve Hansen dumped three veterans - prop Owen Franks and wings Ben Smith and Rieko Ioane, who have a combined total of 213 Test caps.
"I don't think it's a risk and there's lots of reward in it," said Hansen, after opting for the relatively raw talent of Nepo Laulala (18 Tests), George Bridge (three) and Sevu Reece (one).
Even against a New Zealand team built around over 30s, Australia face a huge task in Auckland on Saturday.
They have not tasted victory since 1986 at Eden Park, where the All Blacks are on a 42-match unbeaten streak.
Saturday's Test is scheduled for 09:35 (SA time).
15 Beauden Barrett, 14 Sevu Reece, 13 Anton Lienert-Brown, 12 Sonny Bill Williams, 11 George Bridge, 10 Richie Mo'unga, 9 Aaron Smith, 8 Kieran Read (captain), 7 Sam Cane, 6 Ardie Savea, 5 Sam Whitelock, 4 Patrick Tuipulotu, 3 Nepo Laulala, 2 Dane Coles, 1 Joe Moody
Substitutes: 16 Codie Taylor, 17 Ofa Tu'ungafasi, 18 Angus Ta'avao, 19 Jackson Hemopo, 20 Matt Todd, 21 TJ Perenara, 22 Ngani Laumape, 23 Jordie Barrett
15 Kurtley Beale, 14 Reece Hodge, 13 James O'Connor, 12 Samu Kerevi, 11 Marika Koroibete, 10 Christian Lealiifano, 9 Nic White, 8 Isi Naisarani, 7 Michael Hooper (captain), 6 Lukhan Salakaia-Loto, 5 Adam Coleman, 4 Izack Rodda, 3 Allan Alaalatoa, 2 Tolu Latu, 1 Scott Sio
Substitutes: 16 Folau Fainga'a, 17 James Slipper, 18 Taniela Tupou, 19 Rob Simmons, 20 Liam Wright, 21 Will Genia, 22 Matt Toomua, 23 Adam Ashley-Cooper