Hooker Andrew Hore wasn't too concerned afterwards, but the selectors might not share the same laissez faire attitude. Ben Franks, on for Tony Woodcock at loosehead prop in the second half, struggled at times, particularly when Tonga launched a series of scrums on New Zealand's line.
And with Woodcock not entirely match fit due to his lack of game time in Super Rugby because of a foot injury and recent hamstring twinge, both Franks and John Afoa, another lacking in match minutes, will have to share the load.
"They were really attacking us," Hore said.
"It was pretty tough. We need to close the gaps up, which we can sort out during the week.
"It would be disappointing if we didn't have something to work on at training in the first week of the tournament."
All Blacks' halfback Andy Ellis is likely to play some part against Japan on Friday night after not being required to strip for the World Cup opener. He is expecting another fast and furious start to the match.
"They always go pretty hard, we know that about the Japanese," Ellis said. "They look like they are really well coached and have the players to execute what they are trying to do.
"We see it right across the tournament. You have got guys in good competitions throughout the world and when they come together they are really strong no matter who the team is. We know that about Japan and we are going to have to prepare well."
No 8 Victor Vito believed teams played above themselves at World Cups because of what was at stake and he wasn't surprised by what Japan produced.
"If it was just another game, I think you will find the French would have the better of them but a lot of the time [the World Cup] is the minnows' time to shine," Vito said.
"They grow another arm and a leg and that was indicative of yesterday's performance. In the last 10 minutes the French unravelled it and that was probably the form they should have showed in the first 70 minutes."