South Africa will be without Willem Alberts for their Rugby Championship tour to Australia and New Zealand due to an injury he sustained playing Super Rugby.
Alberts has been replaced in the 30-man squad by Warren Whiteley having missed both Test victories against Argentina because of a hamstring injury.
Alberts underwent a fitness Test on Thursday and although his hamstring is recovering well, he experienced some nerve irritation in his lower back and was sent for scans.
"Willem requires further investigation of the symptoms and will see a number of specialists to determine the optimal management plan to get him back performing on the field as soon as possible," said Springbok team doctor Craig Roberts.
Whiteley, who toured with the Springboks to Argentina last week, will join the team in Johannesburg on Friday morning.
Springbok coach Heyneke Meyer said that although Juan Smith was on standby, the player requested more time to work on his match fitness.
"Juan has very high standards and he wasn't happy with his performance in Salta," said Meyer.
"Warren really impressed me last week, he's been playing very well and it made sense to get him back in. Like Willem, he is very effective with ball in hand and also a great option at the back of the lineout.
"More importantly, Warren is a natural No 8, which is a position where we need cover, but he can play flank as well."
The Springboks play Australia in Perth next Saturday and take on New Zealand in Wellington the weekend thereafter.
The squad will prepare in Johannesburg before their departure to Western Australia on Saturday.
South African squad
Bakkies Botha, Schalk Brits, Marcell Coetzee, Lodewyk de Jager, Bismarck du Plessis, Jannie du Plessis, Eben Etzebeth, Francois Louw, Victor Matfield, Teboho Mohoje, Tendai Mtawarira, Trevor Nyakane, Gurthro Steenkamp, Adriaan Strauss, Marcel van der Merwe, Duane Vermeulen, Warren Whiteley
Damian de Allende, Jean de Villiers (capt), Bryan Habana, Cornal Hendricks, Francois Hougaard, Patrick Lambie, Willie le Roux, Lwazi Mvovo, Ruan Pienaar, Handre Pollard, Cobus Reinach, Jan Serfontein, Morne Steyn