As they entered the quarter-final stage on Saturday, that was arguably the very reason why they encountered the difficulties that they did in a match where they were clear favourites to win.
Had they not been as dominant previously, perhaps New Zealand would have adopted a more expansive approach which would have left gaps for the Samurai Blue to exploit as they did against their previous opponents.
Having seen Japan brush aside South Africa, Mexico and France, OlyWhites coach Danny Hay understandably opted for a conservative game plan. So, for the first time at the Tokyo Games, the Japanese struggled to carve open the opposition defence.
There were a couple of excellent chances spurned when Wataru Endo and Reo Hatate found space at the back post on two occasions and probably should have planted the ball into the back of the net, while substitute Ayase Ueda forced New Zealand goalkeeper Michael Woud into a brilliant point-blank range save in the closing stages.
But after neither side could find the breakthrough in 120 minutes, the last-eight had to be decided by the dreaded penalty shootout.
While it was far from pretty, there were positives for the Samurai Blue to take from a win few would argue was not deserving.
With sharper finishing on another day, they would have wrapped up the last-four berth without needing to even go to extra-time let alone penalties, as they continued to show excellent endeavour in the final third even if they did not create as many clear-cut chances as before.
The Samurai Blue also showcased the impressive depth at coach Hajime Moriyasu's disposal.
Having been dropped for the 4-0 win against France, Daichi Hayashi returned to spearhead the starting XI in place of Ueda and once again offered plenty of enterprise -- even if he is still looking for his first goal of the Games.
Perhaps the main silver lining? Japan are unlikely to have another battle of attrition like this again.
Spain will pose a different set of problems in the semi-finals but they will not be sitting back, and that will at least again afford the Japanese the spaces they excel with that was denied to them by the New Zealanders.
If they get to the final, neither Brazil nor Mexico -- who meet in the other semi -- will be overly defensive as well.
New Zealand posed a test to Japan unlike any other they will face at the Olympics.
And while it may not have been as straightforward as they would have liked, the crucial part is that the Samurai Blue ultimately passed the test to keep alive their medal hopes.