Marx was ruled out of the tournament on Thursday with the Springboks yet to name a replacement, indicating it might not be another hooker.
Loose forwards Deon Fourie (36) and Marco van Staden (28) are covering the hooker position in Sunday’s Pool B clash against Romania, while another flanker Kwagga Smith (30) provides backline cover.
The Boks have 14 backs in France and all but three - centres Andre Esterhuizen (29) and Damian de Allende (31) plus wing Makazole Mapimpi (33) - can play multiple positions.
It is this versatility that allows coach Jacques Nienaber (50) to use a 6-2 split between forwards and backs on the bench, adding grit and muscle to the mix for the full 80 minutes.
Nienaber raised eyebrows when he selected four scrumhalves in his matchday 23 against Romania, but there is method to what some see as madness.
Cobus Reinach starts in the number nine jersey and the speedy Grant Williams is on the wing. Faf de Klerk (31) will come on at fly half and Jaden Hendrikse (23) will replace Reinach.
"From the start, people were wondering why we were taking four scrumhalves but if you look at the versatility within that, that's what we saw," Nienaber told reporters.
"Grant played his school career on the wing, it was only in his last couple of games he moved to nine. A guy like Cobus can help us out on the wing as well.
"Faf played fly half the majority of his school career and for the Lions in Super Rugby and Sale Sharks in the Premiership.
"I'm not being disrespectful to Romania but it's an opportunity to try him out in a test match under pressure at 10."
Nienaber may hesitate to make such selections against a tier one nation, but he is confident the players will perform.
"It's not a risk for us. It is well calculated. We are comfortable with what we saw in training. We believe that the guys are good enough in those positions to beat the opposition."
Damian Willemse (25) makes the switch from fullback to fly half and Nienaber has no concerns about a disruption to the Boks’ vaunted defensive structure in what is a crucial channel.
"If you look at Damian at 10 or Faf, there isn't a problem from a defensive viewpoint. They're brave, they put their heads in dark places. You don't have to hide them on defence."
