South African batting coach Neil McKenzie believes his side need another 70 runs to feel safe after New Zealand captured the key wicket of Dean Elgar to keep alive the prospect of a result in the first Test in Dunedin on Saturday.
At stumps on day four, New Zealand were already sensing a moral victory with South Africa at 224 for six, a lead of 191 and with rain forecast on the final day.
Champion run maker Elgar went late in the day for 89, and if it stays dry, McKenzie said the remainder of the line up needed to build a bigger buffer.
"It's about dictating terms in terms of batting time," he said.
"It's not going to come in 10 overs, that's the nature of the wicket, so we have to graft up front, try and take that lead beyond 260-270 and then you can dictate when you're going to declare."
McKenzie argued that if rain forced a draw neither side could take any extra momentum into the second Test starting in Wellington on Thursday, but New Zealand bowler Jeetan Patel claimed a psychological edge for the home side.
"To be able to stand up against the number three team in the world and beat them on the first innings that's a little win in itself," he said, but adding New Zealand's second innings fielding performance needed improvement.
"We put down a couple of chances which against good side are costly. But, the way the guys kept fighting was pretty impressive."
Elgar was a shining light for South Africa in the gloom of Dunedin as he backed up from a first innings 140.
But on 89 when he tried to lift the pace in the final session, he skied a Patel delivery which was taken by Kane Williamson running to his right from mid off.
On a chilly day in which play was disrupted twice by rain and gloom, Faf du Plessis was on 56 and Vernon Philander on one when bad light ended play 20 minutes early on a tough day which produced only 186 runs and five wickets -- three in the final session -- at University Oval.
While Elgar slowly moved South Africa ahead on the board, New Zealand did not help their cause with a series of blunders, with their problems compounded by the light and a leg injury to Trent Boult.
Boult, who took the wicket of Stephen Cook in the first over of the South African second innings, delivered 11 overs without success on Saturday before leaving the field to join batsman Ross Taylor on the injured list.
When the new ball was taken in the final session Neil Wagner was the only fast bowler available to work with spinners Patel and Mitchell Santner.
Wagner had success early in the day with the wickets of Hashim Amla for 24 and JP for 39.
Duminy had a charmed stay. He was dropped by Tom Latham on six, and on 20 he was given not out to a Patel appeal for lbw.
New Zealand did not review the umpire's decision, although the ball-tracker technology showed it was heading straight at leg stump.
Elgar also had a life when he brought up his half century with a cracking drive that went through the hands of substitute fielder Colin de Grandhomme at short cover.
Temba Bavuma was bowled by Santner for six when he blocked the left-armer only for the ball to hit the pitch and spin back on to the stumps.
Patel then bowled Quinton de Kock (four), claiming the South African keeper for the fourth consecutive innings on this tour.
Patel had figures of two for 72 and Wagner two for 57.