The loss of hooker Malcolm Marx to injury has been a hammer blow to South Africa's chances of retaining their Rugby World Cup title, but coach Jacques Nienaber is taking a 'glass half full' approach as they hold off naming a replacement.

Marx injured his knee in training on Wednesday and has been ruled out of the remainder of the tournament as the Springboks lose one of their most influential players and one of only two specialist hookers in the squad along with Bongi Mbonambi.

"It was a freak accident, his legs just got caught in another player's legs. It was in a contact session, it was a team run and it was just unfortunate," Nienaber told reporters on Friday.

"It's a blow on various levels. When we left Toulon to come to Bordeaux we were all sad. Rugby players work incredibly hard for four years to come to a World Cup, the players sacrifice a lot and their families sacrifice a lot.

"Every individual in our team adds something to the Boks, so we lose that (with Marx). In the mornings I would see Malcolm with his daughter in his arms, so I'm going to miss that and the chats we had."

The Boks are holding off naming a replacement until after their Pool B clash with Romania in Bordeaux on Sunday, with Nienaber saying all options remain open.

That includes a recall for flyhalf Handre Pollard who was injured when the squad was announced in early August, but is on the bench for English club Leicester Tigers on Friday evening.

Manie Libbok has been in excellent form in the number 10 jersey in recent games, but has known issues off the kicking tee, with Pollard, who can also play inside centre, a big influence when the Boks lifted the World Cup trophy in 2019.

"When players get injured you can look at it as the cup is half empty or the cup is half full, and we look at it as the cup is half full, because if there wasn't injuries previously Malcolm wouldn't have (got his chance).

"Handre is in the mix and Luhanyo (Am) is very close to being ready. We will discuss it after the game, we are fully focused on Romania because we should show them that respect."