It may be just another Twenty20 International without a significant trophy up for grabs, but Brendon McCullum insists that New Zealand's clash with South Africa on Wednesday is a "huge match".

The Black Caps skipper believes it could be a "pivotal moment" in the summer, and that intensity has been matched by Proteas captain AB de Villiers saying that his side will be treating it like a final.

South Africa won the second Twenty20 international on Sunday by eight wickets to leave the series level at one apiece, setting up a finale at Eden Park on Wednesday evening.

While the outcome could have a bearing on confidence levels in the three-match one-day series which follows, it should also provide the tension that both teams will encounter at the World Twenty20 later this year.

"I think it's a huge match," McCullum explained. "We have obviously been trucking along pretty good until the last performance when we got hit pretty hard. From our point of view... this is a pivotal moment.

"If we can build on the success we have had this summer already, and manage to win this game and win the Twenty20 series and head into the one-dayers with momentum, then I think we are trending in the right way.

"That's the message I will be delivering to the team today, that it is a big game, in front of 30,000 hopefully in Auckland in a finals scenario, which is pretty exciting."

Sunday's clash saw the arrival of a new star in Richard Levi, who hammered 117 not out off 51 balls to leave the Black Caps in tatters.

"I think it was probably a guy at his absolute best," McCullum said, insisting that the Black Caps won't be too hung up on Levi's knock.

However the Kiwis have been looking at better areas to bowl to the young opener, and have a suspicion that they might be able to get him caught square of the wicket at Eden Park.

One worry is that rain could dampen the affair - although Auckland has enjoyed fair weather recently, showers are forecast for Wednesday evening.

New Zealand are likely to welcome back Jesse Ryder, who was recalled to the Black Caps squad for the third match on the back of a strong run in domestic cricket.

The 27-year-old joined up with the squad at training on Tuesday looking trimmer thanks to a new diet and fitness regime, but while the New Zealand coaching staff have made it clear that they expected Ryder to lose some pounds, McCullum says that his teammate's weight has never been an issue for him.

"I don't really care about his weight," McCullum said. "That's irrelevant to me. It's whether he's capable of scoring runs and contributing to the team in an attitudinal manner as well. When Jesse is going well, he slips into this team brilliantly. He works incredibly hard.

"He's obviously had his issues over the years but, hopefully, there's been some distance put between those incidences. Jesse is a class player. When he's on song, he strengthens our team. That's all I'm worried about."