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McCullum has taken over the reins from Ross Taylor after what he admits has been a trying time for all parties.
"I know it hasn't been a great process, the way it has unfolded," he told journalists in Christchurch today.
But rather than the individual accolade or getting the captaincy, he said his primary concern was for the team.
"The first priority is to make sure we get ourselves together and work out how we're going to win some more games, because ultimately that's what this team needs to do," he said.
"That's got to be our focus."
With Taylor opting for a break rather than go to South Africa and another frontline batsman in Jesse Ryder also unavailable, McCullum knows that it will be a big challenge against cricket's top nation.
Having been made skipper only 48 hours ago, he says he hasn't had a lot of time yet to devise game plans and strategies.
But the 31-year-old doesn't expect the captaincy to change his aggressive batting style.
He says he played on instinct as much as possible and it was when he fought those instincts that poor results arose.
McCullum says he had "absolutely no involvement" in coach Mike Hesson's recommendation to New Zealand Cricket that he take over the one-day and Twenty20 captaincy, while Taylor remained as test skipper.
He said that speculation was the one thing that annoyed him the most as the captaincy issue was played out this week.
"That cuts right to the bone that someone would question your integrity and your character like that," he said.
"I guess it has been mentioned on a number of occasions and, to be totally honest, it's highly insulting."
McCullum said he was asked two days ago if he would be the captain for the shorter formats, and was asked on Friday to lead the test team after Taylor turned down the job.
"That's about as much involvement as I've had in this entire situation."
He also described his relationship with Taylor as "very good" and said it was "media hype and fiction" that it was otherwise.
"Ross is going through some tough times and my thoughts are with him," he said.
"When he is good and ready to come back, then we would certainly welcome him back and I will be looking to try to help him as much as I can to reach the standards that he wants to reach in this game."