A neck injury will sideline flanker Francois Louw for about two months and deal South Africa another blow ahead of Rugby Championship Tests against Australia and New Zealand.
Scrum-half Ruan Pienaar withdrew injured at the weekend ahead of matches with the Wallabies on September 27 in Cape Town and the All Blacks on October 4 in Johannesburg.
Louw and Pienaar, who suffered the injuries during a 14-10 loss to New Zealand in Wellington last Saturday, were automatic starters for the Springboks in the southern hemisphere tournament.
Both are among the growing overseas-based component of the team with Louw playing for English club Bath and Pienaar for Irish province Ulster.
Wing-cum-centre JP Pietersen was recalled in place of Pienaar, but a replacement for Louw is going to be named only later this week, the South African Rugby Union (SARU) said.
The loss of Louw means coach Heyneke Meyer must prepare for the Wallabies and the All Blacks without both first-choice flanks.
Willem Alberts was injured on the eve of the first-round match against Argentina in Pretoria last month and has not played since.
Teboho ‘Oupa’ Mohoje and Warren Whiteley are the loose forward options within the squad that toured Australasia this month, losing narrowly to Australia and New Zealand.
The choice of Meyer will be watched with great interest amid growing government criticism of a national rugby team containing only one regular black African, Zimbabwe-born prop Tendai ‘The Beast’ Mtawarira.
African Mohoje made a brief, impressive mid-year appearance as a replacement against Scotland, but has not had any game time since.
Almost 80 percent of the South African population is African and nine percent are whites, who traditionally fill 12 of the 15 Springboks starting places.
The first-choice wings, Cornal Hendricks and France-based Bryan Habana, are called Coloureds (mixed race) in South Africa.
Title-holders New Zealand lead the Championship with 16 points after four rounds, South Africa and Australia have 10 each and Argentina three.