Coach Scott Robertson said they had their chance against England but were unable to take it.
"We really wanted to get the Grand Slam because we felt it was going to be one of the best ones."
But the reality was that with all the top teams playing in Britain and Europe in November, it was a tough assignment.
"It would have been nice to have kept that alive but we felt like we let an opportunity go."
However, they recovered after a few days and went on to win over an 'incredibly gritty Welsh side.'
Reviewing the season that ended with losses to Argentina, South Africa and England, the lessons were down to fine margins.
Game and referee management will be critical to the side's future.
"We'll get everyone that's involved over the off-season to make sure we do a debrief.
"It'll be good to reflect but it still hurts."
Robertson said he knew when taking on the All Blacks' coaching role that the first two years would be challenging.
There was always the loss of players after a World Cup, but after two seasons, it feels as if they have not yet turned the corner from the loss of experience. They have used 45 players in 2025, so there has been significant exposure to Test rugby, and combinations are developing.
Players like loose forward Peter Lakai and lock Fabian Holland, who has been named World Rugby's Breakthrough Player of the Year, were examples of emerging value.
"Someone like Peter is pretty exceptional. When you get someone good on both sides of the ball, you watch his in-tackle work, his ability to hunt clean, and he doesn't really get penalised.
"He creates so much time for your defence to get set and when he carries his late footwork is pretty exceptional. And Fabian's a story in itself. There's going to be a lot written about him and so there should."
Robertson also backed his captain, lock Scott Barrett.
"I think Scooter's [Barrett] rugby IQ is as good as I've ever come across. He's an exceptional reader of the game. He's unique. He's someone that can push a scrum, call a lineout, make 20 tackles, barge rucks and still make calls and be with the referee. He's done a really good job. We monitor all that."
And he had injury issues during the year.
"All Blacks captain takes a lot of you and he's coming of age with the experience."
He said that no thinking has been done yet on a replacement for departing coach Jason Holland.
"We wanted to get this season out of the way so Jason could leave on a high note, and then we'll look at the market, what we need.
"We'll go through the review and then find exactly what this team needs."
Robertson said he feels he has improved at ensuring the clarity of the messages he gives the side, so they can go out trusting themselves. Some great young players are emerging, and he has had great backing from chairman David Kirk and the New Zealand Rugby board.
The 2026 season will be challenging with the South African tour and the Nations Championship.
"If you want to be the best in the world, you've got to keep playing them. You've got to bring guys through and you've got to challenge them along the way. That's the exciting part for us."
Barrett said after the Wales win that England had pulled the rug from under them in their Grand Slam bid, but the selection for the Wales game had rejuvenated the side with fresh energy.
It was pleasing to see those players take their chances against a valiant Wales unit to finish the tour on a positive note.
Barrett said he thought the team had improved as the season wore on.
"At times, we probably weren't where we would have like to be through key stages but our trajectory as a team is on the way up. There's a big two years ahead of us and the group should be excited about the challenge and the opportunities ahead of us."
