Japan could have been forgiven had they opted to settle for a draw against Spain in their final Group C game at the FIFA Women's World Cup.

Not only was their place in the knockout round already secured prior to Monday's game at Wellington Regional Stadium, finishing second in the group -- which would have been their fate as long as they did not beat the Spanish -- would have handed them arguably an easier last-16 tie against Switzerland, as opposed to a meeting with a Norway outfit who look to be awakening from their initial slumber.

But Nadeshiko are not here to just make up the numbers and be content simply by making it out of the group stage.

They showed just as much by producing a scintillating display that left Spain absolutely stunned, claiming an emphatic 4-0 win to seal top spot with a group-stage record of three wins, 11 goals scored and none conceded.

In an electric -- and ruthlessly economical -- start to the contest, Japan's first three touches of the ball inside the opposition box saw them establish a three-goal lead after 40 minutes.

Despite Spain dominating possession, the Japanese would prove unstoppable on the counterattack with two clinical finishes from Hinata Miyazawasandwiching a deflected effort from Riko Ueki -- who fully deserved a touch of fortune in finding the back of the net for her tireless effort leading the line all on her own.

Although Spain were also already through to the round of 16 ahead of the match, they still fielded a formidable starting XI boasting two-time Ballon d'Or Feminin winner Alexia Putellas, record scorer Jennifer Hermoso and Barcelonastar Aitana Bonmati.

Like Japan, La Roja were also here to win.

Yet, for all the quality in their ranks and possession they enjoyed, they simply could not find a way to break down their well-organised and disciplined opponents, who went on to cap off a stunning victory eight minutes from time through a strike from substitute Mina Tanaka.

Bear in mind that this was a Spanish outfit that not only kept clean sheets in their previous two outings at the Women's World Cup against Costa Rica and Zambia, but had went their entire qualifying campaign without conceding once while scoring a staggering 53 times.

On Monday, their defence was completely exposed not once or twice but four times by a Japan side that have simply been clinical all tournament long.

At first glance, it may be easy to dismiss a win that came on the counterattack as a smash-and-grab, but not with the way Nadeshiko methodically did so with intent -- and credit has to go to coach Futoshi Ikeda.

It is not secret that Japan enjoy having their fair share of the ball but when that was always going to be a tough ask coming up against the Spanish, whose possession-hungry ways are part of their DNA, Ikeda was savvy enough to opt for a different approach.

What is usually an adventurous 3-4-2-1 approach seamlessly transitioned to a more-stable 5-4-1 with the wingbacks dropping deeper, while the two attacking midfielders that usually play centrally behind the main striker moved wider to create two flat barriers that continually repelled La Roja.

Now that they know that it is Norway who they will be facing in the last-16, it will be interesting to see if Japan adopt a similar approach against the tournament's sleeping giants, who failed to score in their opening two games but then sparked to life on Sunday as a 6-0 rout of Philippines sealed their progress.

Even if it is a slightly more conservative setup that Ikeda opts for against the Norwegians, the Japanese have shown that it will be no hindrance to them displaying attacking intent of their own.

And in what is now looking more and more like an embarrassment of riches at Japan's disposal, especially given the attention that was paid to Ikeda's pre-tournament exclusion of star attacker Mana Iwabuchi, it remains to be seen what is now his strongest lineup.

Ueki produced an indomitable display as Japan's focal point in attack -- and first point of the opposition press -- against the Spanish, but that job is usually carried out admirably by Tanaka, who also made an impact by scoring after coming on.

Impressively, Japan's electrifying first-half display was also achieved without Yui Hasegawa -- their regular midfield lynchpin -- while the likes of Aoba Fujino and Hina Sugita should also be staking their claims for a starting XI berth even though they started on the bench on Monday.

The depth at Ikeda's disposal bodes well for Japan, who are now emerging as genuine contenders at the tournament.

Their clash against Spain was their biggest test yet and they passed it with flying colours.

Instead, it is likely that many will now be viewing them as a hurdle of their own -- starting with Norway in the round of 16.