The only players retaining their starting places from the 33-7 victory against the Wallabies at the weekend are backs Cheslin Kolbe, Jesse Kriel and Sacha Feinberg-Mngomezulu, and forwards Elrigh Louw and Pieter-Steph du Toit, who makes a positional move from lock to flanker.
With regular captain Siya Kolisi rested, lock Salmaan Moerat will captain the team for the second time at the Optus Stadium on Saturday while veteran Eben Etzebeth starts on bench.
"We made it clear from the outset this season that one of our main goals is to build squad depth with an eye on the next Rugby World Cup here in Australia," said Erasmus.
"There is no better way to test some of the younger players and assess where we are as a group against a top-Tier nation, especially away from home, in this match."
Lions scrumhalf Van den Berg, 26, made his debut off the bench in the 64-21 win over Portugal last month while Nortje, also 26, has recovered from the knee issue that ruled him out of the Brisbane match and returns for the first time since making his Test debut as a replacement against Wales in Bloemfontein in 2022.
The rotation of players also allows Erasmus to rest some key individuals ahead of the subsequent four Tests in the Rugby Championship against New Zealand and Argentina.
"We have a big squad and it's important to balance some players' workload while at the same time bringing a few young players into the mix, and this squad allows us to do both," said Erasmus, who expects a massive backlash from the Wallabies.
"They will be desperate to come back strongly from last week's defeat and I have no doubt that Joe Schmidt (Australian head coach) will select a team that is fired up and who will give everything to turn things around and get their campaign back on track.
"They are a proud nation and they'll be highly motivated to continue their impressive home win record against us in Australia, so we're fully aware of the challenge.
"This is a massive match for us because if we can build on last week, it will give us a good chance to be in the mix for the title which we last won in 2019."
South Africa team
Starting XV: 15 Aphelele Fassi; 14 Cheslin Kolbe, 13 Jesse Kriel, 12 Lukhanyo Am, 11 Makazole Mapimpi; 10 Sacha Feinberg-Mngomezulu, 9 Morne van den Berg; 8 Elrigh Louw, 7 Pieter-Steph du Toit, 6 Marco van Staden, 5 Ruan Nortje, 4 Salmaan Moerat (capt), 3 Thomas du Toit, 2 Johan Grobbelaar, 1 Jan-Hendrik Wessels
Replacements: 16 Malcolm Marx, 17 Ox Nche, 18 Vincent Koch, 19 Eben Etzebeth, 20 Kwagga Smith, 21 Grant Williams, 22 Manie Libbok, 23 Handre Pollard
