The Official Online RBS 6 Nations Store is open. The store has everything you need to get behind your team during the RBS 6 Nations, plus the store is now fully stocked with a much wider range of rugby merchandise.
The last time O'Gara, who is included on the bench, was dropped was in 2003 and the Lions veteran has had a stranglehold on the position since he returned.
But the composure shown by Sexton in dismantling Fiji on his Test debut has convinced Kidney he is ready to face the world and Tri-Nations champions.
It is a bold selection that rewards the 24-year-old's sparkling form since being thrust onto centre stage during the latter rounds of Leinster's march to their first Heineken Cup crown last season.
Otherwise, Kidney has kept faith with the XV that drew 20-20 with Australia in Ireland's autumn opener with Keith Earls replacing knee injury victim Luke Fitzgerald on the left wing.
Ulster's Paddy Wallace is restored at inside centre where he is preferred ahead of Gordon D'Arcy, who features among the substitutes.
Cian Healy of Leinster resumes loosehead duties after missing out against Fiji because of a shoulder injury.
Munster prop Tony Buckley supplies front row cover from a bench which sees scrum-half Peter Stringer get the nod ahead of Eoin Reddan.
Back row Denis Leamy also features among the replacements despite suffering an ankle injury against the Fijians.
Kidney revealed Leamy will undergo a fitness test later in the week to confirm his place on the bench.
Ireland team to play South Africa at Croke Park on Saturday, kick-off 2.30pm:
R Kearney (Leinster); T Bowe (Ospreys), B O'Driscoll (capt) (Leinster), P Wallace (Ulster), K Earls (Munster); J Sexton (Leinster), T O'Leary (Munster); C Healy (Leinster), J Flannery (Munster), J Hayes (Munster); D O'Callaghan (Munster), P O'Connell (Munster), S Ferris (Ulster), D Wallace (Munster), J Heaslip (Leinster).
Replacements: S Cronin (Connacht), T Buckley (Munster), L Cullen (Leinster), D Leamy (Munster), P Stringer (Munster), R O'Gara (Munster), G D'Arcy (Leinster).