The Springboks are third in Pool B, behind leaders Italy and New Zealand after losing to the All Blacks in their first match of the tournament.
South Africa responded to their loss to the defending champions by thumping Namibia 57-3 and will be expected to get the better of an Azzurri side who have taken maximum points from their two matches.
Yet Italy pulled off a shock when the two nations locked horns three years ago, and although Rugby Championship winners South Africa are a different proposition now, head coach Erasmus says they are nervous given there is so much at stake.
"We've been preparing for 20 or 21 Test matches and it is do-or-die now," said Erasmus, who called Damian Willemse into the squad after Jesse Kriel was ruled out due to a hamstring injury.
"The players feel it. I can't sit here and tell you that we don't have a few butterflies, because we've lost to Italy in the last three years.
"They [Italy] will be really up for this game because they won't believe they can beat the All Blacks, but they will believe they can beat the Springboks."
Tendai Mtawarira, Bongi Mbonambi and Lood de Jager will make up a powerful South Africa pack and Erasmus is expecting a fierce battle between the forwards.
"The challenge that we will get is definitely up front. We do think they have a great backline as well, but we think the physical challenge up front will be scrum-time, mauling."
Sergio Parisse returns to the Italy side and will become the second-most capped player in Test history behind New Zealand great Richie McCaw, taking his astonishing tally to 142.
Italy coach Conor O'Shea said: "The pressure is firmly on South Africa; they are expected to win the World Cup.
"If you don't front up physically against them, you've already lost the match. You must take them on in the forwards. We must treat it like the last match we'll ever play."
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PLAYERS TO WATCH
South Africa - Faf de Klerk
If De Klerk can get quick ball, the livewire scrum-half can control the game and get South Africa ticking to put the squeeze on Italy.
Italy - Sergio Parisse
Skipper Parisse will have a big part to play with his leadership and vast experience. The back-row's battle with Duane Vermeulen should make for great viewing.
Photo Getty Images. Caption: South Africa head coach Rassie Erasmus