South Africa coach Rassie Erasmus warned there were no second chances as he made three changes to the team that lost to New Zealand in their Rugby World Cup opener for the "do-or-die" Pool B match against Italy on Friday.

Prop Tendai Mtawarira, hooker Bongi Mbonambi and lock Lood de Jager all come in for the Springboks' must-win game in Shizuoka.

A second-string Springbok side hammered African neighbours Namibia 57-3 on Saturday, a match for which many of the team that went down 23-13 to the All Blacks were rested.

"This is a do-or-die game for us," Erasmus said. "We have to win this to get into the quarter-finals.

"The players feel it. I'm siting here feeling butterflies because we've lost to Italy recently - they will really be up for this.

"Italy will be the really slippery game for us, like Japan was for Ireland," he said, in reference to the World Cup hosts' shock 19-12 victory over the Irish.

Mtawarira, Mbonambi and de Jager replace Steven Kitshoff, Malcolm Marx and Franco Mostert respectively, who are all expected to make an impact after being named on the bench.

Two players drop out from the New Zealand match-day 23 completely with Trevor Nyakane out of the World Cup with a torn calf and Jesse Kriel nursing a hamstring injury.

In a sign of the Boks' approach to the match against Italy, who have beaten Namibia 47-22 and Canada 48-7 in their opening two games, Erasmus named just two back replacements 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."

The Springboks have met Italy 14 times before, with South Africa winning 13, although that solitary defeat (in Florence in 2016) was with a team featuring 10 of Friday's Bok selection.

"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."

Kick-off is at 11:45 (SA time).

Teams:

South Africa

15 Willie le Roux, 14 Cheslin Kolbe, 13 Lukhanyo Am, 12 Damian de Allende, 11 Makazole Mapimpi, 10 Handre Pollard, 9 Faf de Klerk, 8 Duane Vermeulen, 7 Pieter-Steph du Toit, 6 Siya Kolisi (captain), 5 Lood de Jager, 4 Eben Etzebeth, 3 Frans Malherbe, 2 Bongi Mbonambi, 1 Tendai Mtawarira

Substitutes: 16 Malcolm Marx, 17 Steven Kitshoff, 18 Vincent Koch, 19 RG Snyman, 20 Franco Mostert, 21 Francois Louw, 22 Herschel Jantjies, 23 Frans Steyn

Italy

TBA