South Africa will be without key lock Lood de Jager for their second Rugby Championship Test with Australia in Brisbane on Saturday - one of two changes by coach Jacques Nienaber for the must-win game.
De Jager suffered a concussion in the 28-26 defeat in the Gold Coast on Sunday and his absence will be keenly felt in the second row.
He has been replaced by the less experience Marvin Orie, who will add to his six caps and partner schoolboy friend Eben Etzebeth at lock, in what is the first time they have played together in a Test match.
"Loods' experience will be missed, he has played 50 Tests and Marvin only six," Nienaber said on Wednesday.
"But having said that, Marvin has played with Eben since schoolboy level and has experience in domestic rugby. We trust Marvin as a player and look forward to see what he can bring to the party."
Elsewhere, Prop Trevor Nyakane takes over from Steven Kitshoff at loosehead in the front row, with the latter dropping to the bench in the place of Ox Nche.
"Trevor played loosehead for us in the Argentina Test (earlier in the Rugby Championship) and sustained an ankle injury, but he is now back to full fitness," Nienaber added.
"We all know how well Trevor played for us in the British & Irish Lions series and it's nice to have him back.
"Steven's experience off the bench will be valuable against the Wallabies, who place a big emphasis on the scrums, much like we do."
The Boks are still without wing Cheslin Kolbe, who missed the defeat by Australia with a leg injury.
South Africa will likely have to win their remaining three games in the Rugby Championship to retain the title they won in 2019, which includes the fixture against the Wallabies and then two Tests versus New Zealand.
"We identified the areas in which we need to be more effective this week, and we have been working hard at training to rectify the mistakes we made," Nienaber said.
"The key for us will be to be as competitive as possible in every contest during the match so that we can lay a good foundation to attack from and to use our point-scoring chances."
South Africa: 15 Willie le Roux, 14 Sbu Nkosi, 13 Lukhanyo Am, 12 Damian de Allende, 11 Makazole Mapimpi, 10 Handre Pollard, 9 Faf de Klerk; 1 Trevor Nyakane, 2 Bongi Mbonambi, 3 Frans Malherbe, 4 Eben Etzebeth, 5 Marvin Orie, 6 Siya Kolisi (c), 7 Franco Mostert, 8 Duane Vermeulen.
Replacements: 16 Malcolm Marx, 17 Steven Kitshoff, 18 Vincent Koch, 19 Marco van Staden, 20 Kwagga Smith, 21 Jasper Wiese, 22 Herschel Jantjies, 23 Damian Willemse.