It is unlikely South Africa will declare overnight, but the visitors may come out tomorrow morning and attempt to put on some quick runs and force New Zealand in to batting the rest of the day to avoid defeat.
The Kiwis, who are down 1-0 in the series, will be without skipper Ross Taylor for the rest of the match after he was struck in the arm by a Morne Morkel bouncer shortly after lunch when he was on 18.
New Zealand Cricket medical director Ian Murphy said: "An x-ray confirmed that Ross Taylor has a fracture of the ulna bone of his left forearm.
"The break is not displaced which is a positive sign but we will see an orthopaedic surgeon to determine the best course of action and length of time out of the game.''
South African seamer Vernon Philander, who has been a constant threat to the Kiwis during the test series, claimed 6-81 in New Zealand's first innings in a record-setting performance.
When Philander removed Doug Bracewell for a second-ball duck _ his fifth scalp _ the 26-year-old became the equal second-fastest man to 50 test wickets in the history of the game.
Philander drew level with Englishman Tom Richardson, who also took seven matches to reach the half-century mark, although Richardson completed the feat in 1896.
Philander then dismissed Mark Gillespie for 10 to bowl the Black Caps out, but not before Gillespie edged two balls to the fence for four to ensure New Zealand would narrowly avoid the follow on.
The Kiwis began the day on 65-0 and they looked in a promising position as openers Daniel Flynn and Martin Guptill went about their work.
Flynn, playing his first test since 2009, made a well-crafted 45 and looked assured in the unfamiliar role of opening the batting before he was caught behind by Mark Boucher from the bowling of Philander.
Boucher ended the innings with three catches and although Guptill made 59 he looked patchy throughout his knock as he was dropped twice in the morning session.
Kane Williamson (39), Brendon McCullum (31), Daniel Vettori (30) and Dean Brownlie (29) all made starts but as has been New Zealand's problem throughout the series they failed to kick on to three figures.
The inability of the New Zealand batsmen to put up a big individual score meant they would never get close to South Africa's imposing first innings total of 474-9 declared, which has left them with plenty of work ahead of themselves on day five.
