The veteran duo are set to remain sidelined for Saturday's Nations Championship clash in Durban, and Erasmus revealed that while both players were being considered for a return, lingering niggles convinced the Springbok management to give them another week to recover before targeting next month's one-off clash against Argentina in Buenos Aires.
Veteran lock Lood de Jager and flyhalf Sacha Feinberg-Mngomeuzulu were other players considered for potential inclusion, but Erasmus revealed they ultimately decided against it.
"We were hoping and thinking of playing guys like Siya and so on in this game, but all of them have got a niggle," Erasmus said.
"I know I've been saying week on week that they are really close, but common sense just says next week is off. Then we have Argentina away, and all those guys will definitely be ready for that game."
The Springbok coach said the decision was made with the bigger picture in mind, particularly with a tough away match in Argentina and a four-match Test series against the All Blacks looming.
"We thought, let's wait another week and pick all of those guys for a very tough away Argentina Test match."
The decision comes after the Springboks were pushed hard by Scotland in last week's Nations Championship clash at Loftus Versfeld, with Erasmus admitting there were areas of concern despite securing the victory.
"I don't think we played especially well last Saturday," he said.
"We said before the game that we wanted to win, but the scoreline or result isn't the important thing."
Erasmus identified several periods where the Springboks allowed their intensity to dip, with new combinations and the increased demands of Test rugby among the factors that likely contributed to the performance.
"There was a 20-minute period in the first half and the last 15 minutes in the second half where I thought we slacked a little bit," he said.
"That can be combinations, or it can be that the intensity of the games was a bit higher than some players were used to."
Springbok head coach Rassie Erasmus continues his policy of mass squad rotation in the Nations Championship with 10 changes to his starting XV for the Test against Wales, including four players set to make their debuts.
Springbok coach Rassie Erasmus says Sharks duo Vusi Moyo and Jaco Williams have earned their Test debuts after impressing throughout the national squad's training camp.
SA Rugby revealed that it would thoroughly review its ticketing strategy at the end of the 2026 season, while thanking fans for their continued support during the inaugural Nations Championship.
Stars Vusi Moyo, Jaco Williams, Ruben van Heerden, and Carlu Sadie will all make their Test debuts in the Springboks' third Nations Championship fixture against Wales in Durban on Saturday.
