The Springboks have won the last two global finals in 2019 and 2023, and those successes were built in large part on squad depth.
Performances this year have been largely underwhelming, and on Saturday in Auckland when they lost 24-17, they were their own worst enemies with an error-strewn display.
Erasmus has made seven personnel changes and two positional switches for the second clash with the All Blacks in Wellington this coming weekend.
He said these were not only in reaction to that disappointing showing, but also with the bigger picture in mind.
"It would have been paradise if we’d won last weekend and still made the changes we planned," Erasmus told reporters on Monday.
"Not many players get the chance to face New Zealand away. After this game, the only other opportunity will be after the (2027) World Cup, so the idea was to win and also expose some guys to the pressure of facing the team currently ranked number one in the world."
He did not shy away from the poor performance but said it was not all down to the players.
"We all know a lot of players didn’t perform well, and plenty of coaches, myself included, didn’t coach well last week. One positive was how the game ended. The guys who came on brought energy and fight.
"After 15 minutes we were 14–0 down, but they only scored another 10 points after that.
"We still lost, and that’s the bottom line, but the impact off the bench made me think about bringing in energetic players who haven’t played here before.
"Our main goal is to build squad depth. That means introducing youngsters alongside senior players, giving them opportunities at different venues and positions, and seeing how they develop under pressure."
A key return is number eight Jasper Wiese, who has completed a suspension he picked up for a red card against Italy in July.
"Having Jasper back is a massive plus. He probably won’t play the full 80 minutes, but it’s great to have him in the mix. He’s always been one of our standout players, and for a big test match like this, we’ll need him."