Ireland beat Samoa 17-13 in a rainy Bayonne on Saturday night but celebrations were dampened by Cian Healy's injury scare.
Both the Springboks and the All Blacks have a chance to take over from Ireland at the top of the world rankings this weekend, although the Boks have a much harder task.
Billy Vunipola has been banned for the start of England's World Cup campaign after receiving a three-week suspension for his red card against Ireland.
England suffered a 29-10 defeat at the hands of Ireland, as their World Cup preparations hit another snag, after Billy Vunipola was shown a red card.
Caelan Doris shone and Jack Conan suffered an injury scare as Ireland launched their World Cup warm-up fixtures by easing to a 33-17 win over Italy in Dublin.
Forwards coach Paul O'Connell feels the locks Ireland have selected are 'big' enough to justify the exclusion of Munster star Jean Kleyn.