It will be the 15th match between the two countries and Erasmus has named a strong team for the encounter, with six forwards included on the bench.
“Italy have a very good pack and put a lot of effort in their set phases,” said Erasmus.
“People may think it is a gamble to have only two back replacements, but we want to have plenty of ammunition for what is likely to be a major forward battle.
“It’s a 23-player game these days and the players who come on will be expected to contribute almost as much in game time as those who start among the front rowers.
“But for this game we are asking the players we have chosen to start to set the tone.”
Erasmus said the Azzurri will provide the Boks with a massive challenge on Friday.
“Italy have had their eyes on this match for a couple of years and will have planned and schemed how to bring us down once again,” said Erasmus.
“This is a defining match for them and while we were focusing on the New Zealand game, they will have had their eyes on this one as the key to the quarter-finals for them.
“That means we have to be at our absolute best if we are to beat them – we are at the stage already where there are no second chances. That’s a message we have been emphasising to the players this week.”
Erasmus’s decision to have only two backs on the bench was an option he believed the team had the resources to manage.
“We have versatile players in the backs who can cover a number of positions and we have planned for different scenarios,” he said.
“This game is going to be decided by the forwards and at the set phases and we wanted to maximise our options in those battles.”