Experienced No 8 Duane Vermeulen will join the Springbok team at their Cape Town base on Sunday after missing the opening two Tests against the British & Irish Lions due to an ankle injury.
Vermeulen, who reported for duty briefly at the team's training camp in Bloemfontein in June, has been undergoing rehabilitation following surgery several weeks ago.
However, his steady progress proved to be sufficient for Vermeulen to be called up to the squad that drew the Lions Series one-all with a 27-9 win on Saturday.
"We will never risk a player who is not 100% fit but he brings experience to the squad and it will be great to have him with us."
Nienaber added that the Boks will know more about Pieter-Steph du Toit's injury on Monday.