With the opening game in the balance until just after halftime, Robertson said it was the bench that made a big impact.
"Alex Fidow was a wrecking ball and really opened up some holes in the Australian defence. He gets a crack in the No 3 jersey this week."
Southland's Shaun Stodart also comes in at loosehead prop to join captain Leni Apisai in a new-look front row.
"We've had a few things to work on throughout the week. Our execution really let us down at times during the first match so we want to be more clinical tomorrow," Apisai said.
Another feature of the side is the talented Jordie Barrett at second five. The brother of All Blacks utility Beauden Barrett starred in game one with 15 points and will be partnered by Orbyn Leger on his inside. Leger in turn will partner with his Counties Manukau Under 19 halfback Jonathan Taumateine.
Australian head coach Adrian Thompson has also made five changes to his starting XV, with Melbourne Rebels centre Sione Tuipulotu and Australian Sevens squad member Simon Kennewell brought into the starting XV.
For many players this is the last chance to put their hand up for selection in the squad to go to Manchester in June, which will be announced in the coming days.
"We spoke after the game on Tuesday about lifting our standards across the whole squad after the performance we put out against New Zealand on Tuesday," said Thompson.
"The lads have re-grouped and worked hard at training but we need to translate that to a committed match performance on Saturday night."
You can watch the live stream on www.allblacks.com from 5.50pm tomorrow. Kickoff is at 6pm (NZT).
The New Zealand squad for the World Rugby Under 20 Championship in Manchester in June will be named on www.allblacks.com on Tuesday morning.
NZ Under 20s: Caleb Makene, Malo Tuitama, Sio Tomkinson, Jordie Barrett, Jonah Lowe, Orbyn Leger, Jonathan Taumateine, Marino Mikaele-Tu'u, Dalton Papali'i, Luke Jacobson, Sam Caird, Quinten Strange, Alex Fidow, Leni Apisai (c), Shaun Stodart
Reserves: Asafo Aumua, Ayden Johnstone, Sean Paranihi, Lui Luamanu, Caleb Aperahama, Sam Nock, Stephen Perofeta, Mason Emerson
Australian Under 20s: Jack Maddocks, Simon Kennewell, Liam Jurd, Sione Tuipulotu, Joey Fittock, Mack Mason, Angus Fowler, Maclean Jones (c), Liam Wright, Angus Scott-Young, Ryan McCauley, Izack Rodda, Tyrel Lomax, Joshua Taylor, Faalelei Sione
Reserves: Richie Asiata-Kelemete, Vunipola Fifita, Sham Vui, Rob Leota, Harley Fox, Moses Sorovi, Nick Jooste, Ah-Mu Tuimalealiifano