Erasmus highlighted occasions where Wales had got the better of him during his international career as a player and coach.
“I played in the opening game in the Millennium Stadium in 1999 and they thrashed us,” said Erasmus.
“It was the first time ever we lost against the Welsh and Mark Taylor ran over the top of me.
“My first game as head coach was against the Welsh in Washington in 2018 and we lost. Then the next game here in Cardiff, we lost again.
“In the 2019 World Cup in the semi-final, only three points was the difference.”
Former flanker Erasmus might have been part of the Springboks side beaten by Wales in 1999 in Cardiff, but he was also part of the squad who inflicted a record 96-13 defeat against Wales the previous year.
Many pundits are predicting a heavy Welsh defeat this weekend given the gulf between the two sides but the Springboks coach is not expecting a repeat of 27 years ago in Pretoria.
“I can’t remember much about that 1998 game but then the next year they beat us, that’s how crazy it is,” said Erasmus.
“It was a depleted Wales side back them, a bit like a B team with a lot of injuries. I don’t think it’s going to be anything like that this weekend, it’s going to be a grind.
“What do these guys have to lose? Other than manning up, putting a marker down and saying ‘here we are’ against the Springboks.
“That’s what this Wales team is going to do. Steve Tandy [Wales head coach] looks like he is getting the structures together. We will not be underestimating Wales.”