Easterby said the All Blacks had shown how they dealt with adversity after their Cup warm-up loss to South Africa at Twickenham.
"The opening game against France could have gone either way. They have built nicely over the last couple of weeks in terms of performances and the way they want to play."
While the All Blacks have acknowledged being driven by the loss of their home series to Ireland last year, the Irish have the memory of their quarterfinal exit at the hands of New Zealand in the 2019 Japan World Cup.
Easterby said, "We have experienced so much in the last four years. Those guys who played in 2019 will have gained experience and understanding around different parts of the game, how to approach big games and how to adapt in games. But also, the fresh blood that has come in since 2019 has had unbelievable experiences over the last couple of years."
Part of Ireland coach Andy Farrell's method has been to stress players, to put them in situations to build a back of experience so they would know to draw on it when playing big games.
"There is no bigger game than playing New Zealand in a World Cup quarterfinal. We have been there before, and we were well beaten on that day.
"There were lots of good lessons from 2019, even though it was a different coaching group and different team. There are lots of similarities to their team and ours. That will undoubtedly be an important factor in the game on Saturday."
Ireland knew the All Blacks were hurting from last year's series defeat. But they were concentrating on what they could do better than in their win over Scotland.
"What happened last summer is probably still in the back of their minds – it is only human nature that would be the case.
"But Saturday is a different environment, a totally different game at a neutral venue, and we're going to have to be right on top of our game to beat that New Zealand team."
Knowing that former Ireland coach Joe Schmidt, who did so much to build the side's competitiveness until the 2019 World Cup, was now with New Zealand could work both ways.
"Joe will know plenty about what we're about and individuals in our group.
"But we also have an insight into what they might try to do. It is finely-balanced and it is an interesting subplot to the game itself."
