McCullum admitted the Black Caps were struck by nerves as they went down by 208 runs in the Brisbane series opener, but he said they were back on track after forcing a high-scoring draw in Perth.
The Kiwis get their chance to draw the three-match series if they beat the Australians in the pink-ball Adelaide Test, starting Friday.
McCullum said his team could leave with plenty of respect if they chalked up a win in the first-ever day-night Test, which has caught the imagination of Australian and international cricket fans.
"We walked into this Test series as well prepared as we thought we could be but just a little bit nervous and I think that affected the way we were able to execute our skills.
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"Credit to Australia. They put us under a lot of pressure early on. It was a combination of us not being quite at our best and Australia playing really well."
"I think we've seen a team which is operating a little closer to where we expect ourselves to operate on a daily basis," he said. "There are certainly some encouraging signs. We've got to get better in this Test match as well because Australia will ask some different challenges of us again.
"If we can pull off a Test match victory here we leave Australia reasonably content with our work.
"We came over here to win the series, but that now is off the table but we can certainly leave with a lot of respect and a drawn series which would be a very good achievement against a new and emerging Australian side."
"Batting-wise I probably haven't been at my best in this series and I feel as if I can get past those first 20 balls then you can make an impact," he said.
"And what a game to do it in in the third match of a series against a very good Australian team in their own conditions in the first-ever day-night Test match."
McCullum did not name a team, saying key fast bowler Trent Boult's back complaint would be further assessed on match morning.
Talking about New Zealand's performance on the tour of
India, McCullum said the young team will learn a lot out of this experience.
"Look India is always a tough place to tour. It is incredibly difficult here, the conditions are so different to what we have back home. I think the guys will take a lot of learning out of this tour. I am sure in time we will see the benefits of how tough this tour has been for the boys," he said.
"It is just the nature of touring India. What we are brought up on, the wickets and the conditions, are so different from what you get here. So it is a matter of trying to adapt as quickly as possible. I think some of the guys did that, especially Latham (Tom). I think he has been outstanding through out the tour in a really tough position (opening).
"Kane (Williamson) also got some runs and he is required to score a lot more. In the end, you are not going to come over here and have instant success. As long as you are taking the learnings out of this experience, and continue to develop your game when you leave these shores, I think that is really important for a young team," he said.
"I think Kane is going to be an incredible leader. At such a young age, he is already very mature. He is a world class player. I think the team is just finding itself in tough circumstances and you just have have to be careful that we don't judge them too harshly on this tour because it is a tough place to come to. I am sure over the coming months, the leadership which is in place will stand up in their own conditions," he said.
So has there been any positives from the tour?
"Latham's batting has been a huge positive. Luke Ronchi is a big positive, I thought the bowling group stuck to their tasks really well too. Again early stage for spinners Ish Sodhi and Mitchell Santner but I thought they performed really as well. I think the other thing is that India are the number one Test team in the world. It is not easy come over here and compete against them."
"I was skeptical about its existence at the outset when we played the debut match. But I think if you look at the success of that and the last couple of games, we have seen exciting finishes. As long as you get the pitches right for the different ball (pink ball), after all day night cricket is about the ball which is meant to allow you to play cricket in the night. As long as we have that, it is an outstanding acquisition for the cricketing fraternity," he said.