In the minutes following New Zealand's crushing defeat of Sri Lanka in the tournament curtain-raiser, Corey Anderson let slip a word that may have caused mild discomfort within the New Zealand camp. He said that before that match, Brendon McCullum had asked his charges to "go about our work and keep what, I guess, we've begun as a juggernaut - to keep rolling forward."

Maybe it was nothing more than a slip of the tongue: a word Anderson had used with no intent to intimidate. But as this New Zealand team has breezed around the country collecting bested opponents, it has been easy to see the juggernaut in them.

They haven't just impressed with the frequency of their wins, but also with the manner of their unfolding. Daniel Vettori strikes when the new-ball bowlers have not cut through the top order. Top-order collapses are no more than a chance for the men lower down to show their wares. Already this year, New Zealand have broken the sixth-wicket partnership record in both ODIs and Tests. In another match, New Zealand were 101 for 5 chasing 219, before Corey Anderson shelved aggression and embraced measure, to stroke the 96-ball 81 that would win them the match. Their fans, no surprise, have never flocked in such quantities or been in better voice.

But as Scotland made dents to the hosts' order in defence of 142, a little of the old, unsteady New Zealand side peered through their shiny new armour. This used to be a team for which no match situation was safe. Who, not so long ago, were cleanswept in Bangladesh. They are now hailed by some as the best New Zealand team ever, but no more than three years ago, talk-back radio suggested they were the worst in 50 years.

Scotland were spirited for sure in the field, adding beef to the argument that the ICC has blundered in pruning the 2019 World Cup to 10 teams. In truth, Scotland were never really in the match. The chance off Brendon McCullum, with the team score on 22, might have spurred them to a better result, but that catch was grassed, and though four wickets fell in a rush toward the death, each dismissal seemed 20 runs too late. Yet, for the first time in weeks, their pacemen had managed to shake New Zealand.

"It got a little scarier than we wanted, I guess," Trent Boult said after the match. "When I'm rushing around the changing room trying to chuck the pads on, it means we might be in a little bit of trouble."

New Zealand may have suffered from lack of intensity chasing such a meagre score, against such inexperienced opposition, but it is possible that the team's batting is more vulnerable than recent results have suggested. They must know there are greater peaks to be scaled before a real bid for the World Cup can be made.

The Sri Lanka attack, which New Zealand bossed during the 4-2 series win, for example, was without spearhead Lasith Malinga. In any case, Sri Lanka had only played three frontline bowlers for much of that series, and Angelo Mathews was also unavailable for three of the six completed games. Even when Malinga returned for the World Cup curtain-raiser, injury appeared to have eaten at his pace, and his accuracy. Pakistan had threatened with Mohammad Irfan in patches during the two-match series preceding the World Cup, but otherwise fielded a green attack.

So in the next two matches against England and Australia attacks that appear to be better than those they have faced - perhaps in months - the top order has questions to answer. Can McCullum's hyper-aggression be successful against bowlers who seam the ball more adeptly than the South Asian quicks? Can Kane Williamson's form persist when fielders do not routinely grass chances off his blade? Do Ross Taylor's travails spread beyond the nerviness against spin that has regularly ensnared him, including against Scotland's Majid Haq?

Elsewhere, Martin Guptill has only hinted he has shaken the bad run that saw him collect two golden ducks in three innings. Luke Ronchi and Grant Elliott have been outstanding when early wickets have fallen, yet again, they weren't hemmed in by skilful bowlers during the middle overs.

"I think the game showed that New Zealand's batters were vulnerable if you're able to keep them under pressure consistently and put the balls in good areas, as any batter is," Scotland captain Preston Mommsen said. "But at the same time, chasing out a small total might have been a little bit tricky for them. It might have changed the way their natural game would usually be. I'm not sure what other teams will make of it."

New Zealand have deserved their hot streak, and arguably, no one plays more attractive cricket than them at present. The 13-over period in which they lost all batsmen from Williamson to Ronchi has been the only glimpse that overconfidence has begun to set in. As almost every member of their squad stresses, they would be wise to "not get too far ahead of themselves" just yet.

Andrew Fidel Fernando is ESPNcricinfo's Sri Lanka correspondent. @andrewffernando