Captain AB de Villiers was particularly hard on himself after South Africa slumped to a six-wicket defeat to New Zealand in Friday's first Twenty20 International in Wellington.

Batting first on a Westpac Stadium pitch that home skipper Brendon McCullum admitted was two-paced, the Proteas struggled to 147 for six.

Their final score would have read considerably poorer were it not for the four consecutive sixes that Justin Ontong smacked off the bowling of part-time spinner Kane Williamson, but a largely inadequate tally was due to the failure of the top order.

Richard Levi managed just 13 on debut, Hashim Amla's promising 19 was ended by a run-out, Colin Ingram was stumped for a duck and de Villiers survived an early stumping opportunity before holing out on the off-side.

The visitors were struggling at 52 for four and, bar Ontong's blitz, never really recovered. The Black Caps reply was a fluid effort, with Martin Guptill's 78 not out - his sixth consecutive half-century in international cricket - carrying his side to triumph with four deliveries to spare.

While the Kiwis had succeeded thanks to a bowling attack lined with four slow bowlers, the Proteas only had two to call on, neither of which were tight enough to undo Guptill's five-boundary, four-six onslaught.

"We did it not start well, especially myself," rued de Villiers. "That put a lot of pressure on the rest of the boys. We came back reasonably well and I thought we fielded well but I made a couple of mistakes captaincy-wise.

"We weren't surprised New Zealand opened their bowling with a spinner and then had more to follow. We expected something in that line from them and we should be professional enough to adapt.

"Our bowlers bowled well but they had too little to defend. We played well in patches and we will look to do well on Sunday."

The right-handed Guptill, who was also responsible for the run-out of Amla and the superb catch that got rid of de Villiers, was named Man of the Match for his all-round performance and duly fetched high praise from his skipper.

"Martin is in the form of his life and he made this chase look easy. The pitch was two-paced at times and the ball was stopping a bit on the bat," added McCullum. "We will look to do well in the next match. We pride ourselves in the field and we have done very well in this series so far."

The second T20I of the three-match series gets underway in Hamilton on Sunday.