Fleming countered criticism of his decision to bat on into the third day. He said the best chance of winning had been to force South Africa to follow on.
"I needed everything I could get. I probably needed more. The follow on was our only real chance. We had to bowl South Africa twice. When you commit to that you have to get enough cash in the bank."
He said it might have been better to let James Franklin and Jeetan Patel continue their free-scoring unbeaten ninth wicket partnership of 58 for another half hour.
"It might have been given us more cushion but we thought we had enough overs to bowl them out."
South African captain Graeme Smith said he was surprised New Zealand had batted on so long, "especially the way the Test match had gone with light in the evening and dew in the morning. They went past a point of having to make a game of it, they had to try and make us follow on."
South Africa responded by scoring 512, with centuries by Hashim Amla and Ashwell Prince, batting until after lunch on the final day. New Zealand were 121 for three when bad light ended the match.
"We all want results but when you are put in a corner you have to play the situation," said Smith. "We're 1-0 up in the series. We were forced into being defensive and getting through this game and that's what we did."
Smith said South Africa would look to play more aggressively in the third and final Test starting at the Wanderers in Johannesburg Friday. "We want to play positive cricket, winning cricket," he said.
"We felt it better to grind their bowlers into the ground with the next Test starting three days later. It gave us a great opportunity to go to the Wanderers with a bit of momentum. The batters have got runs under their belt.
"I'm sure the wicket there will be a little more juicy. It always has a bit more of a result in it than most other wickets."
Fleming said New Zealand were disappointed not to have a chance of winning the series. He said personal satisfaction at his own man of the match innings of 262 was tempered by the lack of a win.
"It's disappointment because we came here to win a series. We created some opportunities in this Test and couldn't convert."
He said New Zealand were determined to try to level the series by winning in Johannesburg. "It should be a result wicket. There's been a lot of inclement weather up there and hopefully we can get on the right side of it."
With virtually no chance of an outright result, the highlight of the final day was the left-handed Prince reaching his fourth Test century.
Prince batted patiently on a pitch which again offered no help to the bowlers. It took him almost two hours to move from his overnight score of 70 to his century, which he reached with a straight drive for four off New Zealand left-armer James Franklin. He had faced 259 balls and hit nine fours.
There was brief excitement at the start of the final day when Franklin, who made a century batting at number nine in New Zealand's first innings, struck twice in two balls in the fourth over of the day after South Africa resumed at 427 for five.
But Andre Nel and Dale Steyn supported Prince as South Africa batted on past lunch. Franklin finished with three for 95.
Left-arm spinner Daniel Vettori claimed his second wicket of the innings when Steyn was stumped. It was Vettori's 218th Test wicket for New Zealand, putting him joint second with Chris Cairns on the country's all-time list, behind Richard Hadlee, who took 431.
South Africa won the first Test at Centurion by 128 runs.