South Africa's Malcolm Marx out of Rugby World Cup with long-term knee injury

South Africa hooker Malcolm Marx was ruled out of the remainder of the Rugby World Cup on Thursday with what the team described as a long-term knee injury.

Marx sustained the injury in a training session on Wednesday when his knee was "caught in contact," the Springboks said.

The team didn't immediately give any more details on the exact nature of the injury but suggested Marx was facing a long time on the sidelines.

"He's been working very hard to be in the best form possible for the tournament and it's tragic that his campaign has ended this way," coach Jacques Nienaber said.

It's a blow to the defending champions' chances of retaining their title in France, with the 29-year-old Marx one of the form players in the team. He was also part of the 2019 title-winning squad.

South Africa has just one other specialist hooker in the squad in Bongi Mbonambi, who was selected to captain a second-string Springboks team against Romania on Sunday.

However, South Africa also selected 36-year-old utility forward Deon Fourie in its squad, who can play hooker as well as his most recent position of flanker. He had already been picked to be the reserve hooker against Romania.

Nienaber said Thursday that loose forward Marco van Staden also had previous experience at No. 2 and might be called on to play there.

"We have enough cover at hooker with Bongi (Mbonambi) and Deon (Fourie) in the squad, while Marco (van Staden) has also been training there and has been named on all our team sheets so far as a hooker option," Nienaber said. "We'll assess our needs for the rest of the tournament and confirm who we are calling up as an additional player later this week."

"First and foremost, we are extremely disappointed for Malcolm and we wish him all the best in his recovery."

South Africa said the injury replacement for Marx wouldn't join the squad immediately as it had sufficient cover for now.

South Africa also has an injury concern over lock Eben Etzebeth, who was replaced in the first half of the win over Scotland last weekend with a shoulder problem as the Boks opened their title defense. The Springboks expect him to be out for 10 days but hope he'll recover in time for a highly-anticipated pool game against top-ranked Ireland on Sept. 23.