New Zealand captain Brendon McCullum feels his team have put down a marker with their convincing six-wicket victory over South Africa in the first Twenty20 in Wellington.

The Black Caps outthought the Proteas in the field to restrict them to 147 for six in their 20 overs, and then opener Martin Guptill followed it up with 78 from 55 balls to lead his side to a comfortable win.

McCullum was naturally pleased with his side's efforts as they proved that they can beat any side in the world.

"It was a huge game for us. Everyone in the country was probably wondering if we could carry on the form from the Zimbabwe series against a higher quality opposition. Tonight was a great statement from us," said McCullum.

"But we'll talk tonight about expecting South Africa to improve. We'll enjoy [the win] in the changing room for about half an hour, but then we'll turn the focus onto the next game."

Much of New Zealand's success in the opening T20 was down to their ability to restrict South Africa's top order from scoring quick runs.

The visitors were stuttering at 52 for four after nine overs before JP Duminy (41) and Justin Onting (32) gave their bowlers something to defend.

"They've got some dangerous hitters down the order and if you let them strike from a platform then they can be quite unstoppable, so there was a need to take early wickets," added McCullum.