Pienaar has been ruled out for up to six weeks, first-choice Fourie du Preez will miss the rest of the season following shoulder surgery and his regular deputy Enrico Januarie was dropped following poor performances in the two Tri-Nations matches against New Zealand.
De Villiers, who names his squad for the home Tri-Nations matches on Sunday, may be forced to start with the inexperienced Francois Hougaard, who has only made two test appearances as a replacement.
Other players ruled out by injury or suspension include locks Andries Bekker and Bakkies Botha, and centre Jaque Fourie.
South Africa's hopes of defending their Tri-Nations title are all but over after three successive losses. They host the All Blacks in Soweto on Aug. 21 and Australia in Pretoria on Aug. 28 and Bloemfontein on Sept. 4.