Le Roux, who earlier this season became just the eighth Springbok to reach 100 Test caps, was set to start at No 15 but picked up the issue during training and failed to recover in time, opening the door for Fassi to step into the starting XV.
Fassi, 26, will be making his 14th Test appearance. Known for his counter-attacking flair and aerial skills, the Sharks star has been in and out of the national setup since his 2021 debut but has impressed Erasmus with his form this season.
Springbok captain Jesse Kriel says his team has learned their lessons from last week's defeat to the Wallabies and are determined to set things right when the sides meet again.
All Blacks hooker Codie Taylor honoured those who have come before him as he prepares to earn his 100th cap on Saturday against Argentina.
Hooker Codie Taylor will become the 14th All Black to reach 100 Test caps when he runs out against Argentina for the second round of the Rugby Championship.
Argentina head coach Felipe Contepomi has made just two changes to his starting team for their Rugby Championship rematch against New Zealand in Buenos Aires on Saturday.
