The Wallabies are counting the cost of a physical Test against the Springboks after picking up a series of injuries in the 33-7 defeat.
Winger Filipo Daugunu is the most serious, suffering a fractured fibula in the opening minutes.
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Daugunu was replaced in the 25th minute of the defeat by Dylan Pietsch after emerging as one of the Wallabies' best during the July Tests.
Locks Nick Frost and Jeremy Williams also picked up concussions in the loss, with Frost's eye nearly closed shut as he wore the scars of a tough contest.
Williams meanwhile lasted just 12 minutes before suffering the head knock and will miss the Wallabies' return to WA amid the 11-day stand-down policy.
Josh Canham will join the squad as cover for the pair and is line for a potential debut with Angus Blyth and Tom Hooper amongst the options to come into the 23.
Canham recently linked up with the Queensland Reds and impressed in the matches against Wales and Tonga.
Force duo Sam Carter and Tom Robertson will also come into the squad as further numbers in the lead-up to the Test.
Prop Taniela Tupou will return to Tonga for his father's funeral after missing the loss to South Africa and is a chance to re-join the squad in time for Saturday's Test.
Schmidt hinted after the game at his desire to keep a settled squad, although will now be forced into changes.
“We’ve got a much younger sit and a lot less caps and therefore my belief is if we chop and change too much then it’s very hard to grow the cohesion. When you go out in a game like that, you’re very interdependent and you’re going to have to make sure that everyone know their role has been built ready to deliver," Schmidt said.
“I thought Carlo Tizzano did really well today but would’ve been nice to have Fraser McReight as well and then you have Luke Reimer coming off the bench so there’s guys that will get better with opportunity.
“…I’m a realist and I know that you don’t suddenly match up and front up but you’ve got to better yourself for next week.”
