South Africa hooker Malcolm Marx will miss the rest of the World Cup because of a knee injury suffered in training.
The 29-year-old, who has won 64 caps, sustained the injury "in contact".
"We are extremely disappointed for Malcolm," said coach Jacques Nienaber. "It's tragic that his campaign has ended this way."
They now have only one specialist hooker - Bongi Mbonambi - in the squad.
"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," said Nienabar.
"We have enough cover at hooker with Bongi 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."
South Africa also play Ireland, the world's top-ranked side, and Tonga in Pool B.