The Springboks have made nine changes to their XV and Argentina five as both give minutes to their wider squad ahead of the global showpiece tournament, which gets underway on September 8th.
New Zealand lead the Rugby Championship table with nine points going into their clash with struggling Australia in Melbourne.
South Africa have five and Argentina four, so for either to lift the trophy, they need a big win and to hope the All Blacks are well beaten too.
The world champion Springboks are perhaps most in a quandary over World Cup places with the battle to be on the plane to France a fierce one in many positions.
Malcolm Marx finally gets his chance to start at hooker this weekend, the first time this season, but Bok coach Jacques Nienaber says it is all about managing minutes.
"Our challenge is to spread that load between the squad," Nienaber told reporters.
"We don’t want to go cold into Scotland in that first game at the World Cup with one or two guys having most of the minutes.
"If you pick up an injury or two, you are bringing in a guy that is cold. That is the balance that we would like to have."
It means the Boks have yet to select what many would consider their best XV in 2023, and for players like centre Jesse Kriel, scrumhalf Grant Williams and flanker Marco van Staden, this is a major opportunity to impress.
Argentina coach Michael Cheika has also shuffled his backline, making four changes from the 34-31 victory over Australia in Sydney, with a further forced change at lock due to an injury for Matias Alemanno.
Centre Santiago Chocobares starts his first test since 2021 and Juan Cruz Mallia gets a first run at fullback this year as Argentina seek a maiden win at Ellis Park.
"Mallia, Chocobares and Juan Imhoff played in the final stages of the (French) Top 14 and that's why they had a break," Cheika said.
"But it is the right time to give them a chance, along with (prop) Joel Sclavi, who is a replacement."
The teams will meet again in a World Cup warm-up game in Buenos Aires on August 5th.