Gary Stead is backing Colin Munro and Martin Guptill at the top of the order as New Zealand aim to bounce back from their first loss of the World Cup, against Pakistan.

The openers have struggled to make runs since their first match of the tournament and there has been speculation that one of them could make way for Henry Nicholls against Australia at Lord's on Saturday.

But Stead played down the chances of any changes, pointing to Nicholl's relative inexperience opening the batting. Nicholls has batted in the middle order for most of his ODI career, although he opened in four matches earlier this year against India and Bangladesh.

"He's definitely an option but Henry hasn't done a lot of [opening] either," said Stead. "But Henry's definitely an option we'll consider.

"We'll review it again when we get down to London but there are only 15 players here and you pick people to do certain roles as well. We have to balance up current form with, I guess, the roles that we are trying to play with the guys."

An unbroken Guptill and Munro partnership successfully chased 137 against Sri Lanka at the start of New Zealand's campaign but since that match the returns have been comparatively slight. Guptill has made two ducks and a total of 65 runs in five innings since that and Munro's numbers have been similar; one duck and 67 runs.

"Look it's no secret, Colin and Martin got away to a great start in the Sri Lankan game and runs have been a bit scarce since then," said Stead. "But they're not the only openers in the competition that haven't got runs and we only have 15 players in the squad. So you start weighing up what does that look like in terms of changing too much in the team and that's something we certainly don't want to have, wholesale changes everywhere in our order."

There is no disputing Guptill's value at the top of the order - he averages a tick under 43 in 175 ODIs - and while Munro averages a more modest 24.92, his explosive hitting in the Powerplay has given New Zealand rapid starts in the past.

"There's no doubt that if he does do that then he can change the game really quickly," said Stead. "So again that's part of our thinking and our hope that can be the case. You saw against Sri Lanka what Colin and Martin can do if they get in.

"It's getting later on in the tournament and it hasn't happened regularly but that's cricket. We can't have everything go our way, the way we want, because if they batted very well you wouldn't be able to see the skills of Kane Williamson on order either."

That last comment was made with tongue-in-cheek humour, of course, but New Zealand have relied on Williamson and Ross Taylor to shore up the innings after early losses several times throughout the tournament. Stead said the openers weren't trying to be overly aggressive rather than set up a solid base.

"We are trying to do that we are trying to get a base," said Stead. "But sometimes you get good balls or you're a little bit out of form and those things happen in cricket.

"Colin hasn't got off to lightning starts in any of the games, he's just trying to play good cricket shots and that's just all our guys try and do all the time."

New Zealand has yet to cement a semi-final berth and next face Australia, a side very much on a roll, before taking on what could be a desperate England side, fighting for a place in the top four.

"I never expected we'd go through the whole tournament, play and be unbeaten," said Stead. "There's only one team that's like that at this stage and that's India and they are a very good team as well so I think when you play nine games in a round robin and you look at the numbers, there's maybe five or six games you need to win, that's ultimately our target first up."

A defining feature of Australia's victory over England at Lord's was their decision to play and open with two left-arm quicks, a masterstroke that paid off with Jason Behrendorff taking five wickets and Mitchell Starc collecting four. Stead expects Australia will also take note of Pakistan's successful tactic of opening with left armers Mohammed Amir and Shaheem Afridi, who bowled a particularly destructive new-ball spell.

"In some ways it's good because Pakistan had three seamers against us and we probably expect, after Behrendorff's success at Lord's as well, that he's likely to play again," said Stead. "We certainly won't take that for granted but we'll plan to have two left armers play against us. But it's good we've had that, I guess, exposure to left armers, in the last game. But this is a completely new wicket and a different surface and part of what we try to do is adapt to different situations and hopefully we can do that in this next game.

"I also think that our bowlers have done a really, really good job for us so far and the talk here before we came into this tournament was that they were all going to be 350 wickets and we haven't had one close to that so I think your bowlers are the guys who will keep us in the game and if we play well as a team then we think we are every chance against Australia."