South Africa brought back batsman Ashwell Prince in place of spinner Robin Peterson from their line-up which beat Sri Lanka by one wicket in their first Super Eights match last week.
Ireland, who lost their first Super Eights match to England, brought in Paul Mooney for Kevin O'Brien.
Overnight rain and wet outfield delayed the start by one-and-half hours.
Pollock delivers early blows: SA seamer Pollock makes early inroads into Ireland top order to leave them reeling on 63-3 after 20 overs after two lengthy rain delays, the match had been reduced to 35-overs-a-side.
Niall O'Brien was 16 not out with Andrew White was on nought.
Opener Jeremy Bray fell lbw to Shaun Pollock for nought in the third over before William Porterfield became the second batsman out, caught by Jacques Kallis at extra cover off Pollock for 14.
Eoin Morgan was the third man out in the 20th over caught by Ashwell Prince off Andrew Hall for 28 with the score on 23.
Ireland: William Porterfield, Jeremy Bray, Eoin Morgan, Niall O'Brien (wk), Andrew White, Andre Botha, Trent Johnston (capt), Kyle McCallan, Paul Mooney, Dave Langford-Smith and Boyd Rankin.
South Africa: Graeme Smith (capt), AB de Villiers, Jacques Kallis, Herschelle Gibbs, Ashwell Prince, Mark Boucher (wk), Justin Kemp, Shaun Pollock, Andrew Hall, Charl Langeveldt and Makhaya Ntini.
Umpires: Daryl Harper (Aus), Simon Taufel (Aus) and Third umpire: Mark Benson (Eng).
Referee: Ranjan Madugalle (SL)