South Africa had fast starts in all three of their Nations Championship Tests but in their opening two matches they let Scotland and England back into the game.
Those two sides dominated the second quarter in both of those matches before the Boks managed to regain their composure and claim victories.
There were fears that history could repeat itself after the hosts raced into a 14-0 lead in Durban before the Welsh stemmed the bleeding.
However, their tryline remained intact and the Springboks would go on to register a dominant 43-0 victory at Kings Park Stadium.
"It was a concern but on Saturday when we were there we squeezed through and we didn't let them in," Erasmus said.
"We managed to keep the pressure on. We buggered it up in the first two games and we did it against Australia last year as well, but we fixed it in this game.
"It starts to creep into your mind a little bit - is this going to happen again? - and then the communication between us and the players on the field, stick to what we're doing and we managed to get through it.
"It was almost there again but it didn't happen."
Erasmus decided to once again change up his squad, playing some first team regulars but also mixing it up by giving a few players opportunities.
Four players made their Test debuts in Carlu Sadie, Ruben van Heerden, Vusi Moyo and Jaco Williams, while individuals such as Cobus Wiese and Paul de Villiers were handed another chance.
Despite the alterations, South Africa proved far too strong for Wales to leave the head coach "satisfied" with the performance and the start to their Nations Championship campaign in general.
"You could see they were up for the defence so to get 43 points and keep them to nil, we're satisfied. The four debutants playing their first matches and obviously guys like Cobus Wiese and Paul (de Villiers), they're not he regular guys who play for us," Erasmus said.
"The only guys who we say play a lot for us are Cobus (Reinach], Jesse (Kriel], Kurt-Lee (Arendse], Doogz (Damian de Allende] and so on.
"It was definitely better than last week, especially defensively, although it's easier to defend on wet field.
"No injuries, that's the first time after a game we can say no injuries, so that's good."