The Springboks are the only major rugby union nation coach Stuart Lancaster has not beaten in his time in charge, with their best result a 14-14 draw in Port Elizabeth two years ago.
In fact, England have a pretty dismal recent record against the Springboks, with their last win coming back in 2006. Since then, the Boks have won 10 out of the 11 matches, with the draw in PE England's only positive result.
"(A win) will be huge for this group," Robshaw told BBC Radio 5 live.
"We've never beaten them, so I think it will be a huge stepping-stone for us."
After losing at home to the All Blacks last weekend, and with the Rugby World Cup just 10 months away, Robshaw admitted that the tournament's hosts have to start delivering against the best teams in the world.
"They are all must-win games at this international level," he said.
"We need to really impose ourselves, being at home, and we have a chance to do it (on Saturday)."
England will name their team later on Thursday.
Kick-off for Saturday's clash is scheduled for 16:30 (SA time).
Teams:
England:
TBA
South Africa:
15 Willie le Roux, 14 JP Pietersen, 13 Jan Serfontein, 12 Jean de Villiers (captain), 11 Bryan Habana, 10 Pat Lambie, 9 Cobus Reinach, 8 Duane Vermeulen, 7 Schalk Burger, 6 Marcell Coetzee, 5 Victor Matfield, 4 Eben Etzebeth, 3 Jannie du Plessis, 2 Adriaan Strauss, 1 Beast Mtawarira
Substitutes: 16 Bismarck du Plessis, 17 Trevor Nyakane, 18 Coenie Oosthuizen, 19 Bakkies Botha, 20 Teboho “Oupa” Mohoje, 21 Francois Hougaard, 22 Handré Pollard, 23 Cornal Hendricks