Having faced criticism over his caucus' Māori representation, Bennett's resignation gave Muller a chance to reassess. He had said he would "consider" it, but in the end the weight given to Māori remained the same.
Dr Shane Reti was promoted from 17 to Bennett's number-13 spot, also taking Bennett's Treaty of Waitangi negotiations role but relegated to associate spokesperson to Amy Adams' drug reform portfolio.
Meanwhile former leader Simon Bridges boomeranged back into the National Party's top 20, taking the foreign affairs portfolio off senior MP Gerry Brownlee - a role he had been rejected for after losing a leadership contest to Muller - and slipping into Dr Reti's newly vacated number 17.
Speaking to RNZ's Checkpoint on Thursday, Muller was adamant there was no bad blood between him and Bridges.
"I was under the impression at the time that he was reflecting on what happens next, and obviously he made it clear - and I'm delighted that he has, actually - that he wants to stay as an MP and made actually a very determined decision.
"You deal with what's in front of you... and with that opportunity to promote of course Shane and give Simon a job that of course he wants, but more critically will hold the Minister of Foreign Affairs to account - and I can't wait to see that."
He denied that meant he thought Brownlee was not up to the job.
"Of course he was... you make judgments around how to frame up your team in the context of a small, minor reshuffle. Gerry's got a lot on in terms of obviously shadow leader of the house and particularly he's running our campaign - he's got 10 weeks to go there.
"Simon's got a huge amount to offer so I took the moment and thought I'd give him that opportunity."
Nor was it a case of keeping one's enemies close, he said.
"Not at all ... I mean, clearly I challenged for the leadership, that was robust, but we've a professional relationship, we're side by side in the same city so you don't need to worry about that, [we] certainly know how to work together for the good of this country and you'll see that demonstrated in spades over the next few years."
He was dismissive of suggestions the number 17 ranking did not befit the mana of Bridges' new portfolio.
"Simon reflects the mana of the portfolio... there's a lot of focus on what the numbers are this side of the election but look, we've got a campaign to run.
"We're a team of 55 which, you know you've heard me say it before but frankly bests the other side when you have a Health Minister resign and the portfolio given to an Education Minister who's already run off his feet. That's their problem - they've got no depth. We've got depth, we're going to run hard to the election and we'll see who's in what seat by the end of it."
He was also complimentary of Dr Reti, a former GP who Muller's critics had said was a clear choice for the health portfolio.
It was a minor reshuffle, Muller said. "We're 10 weeks out from the election, running hard and I had the opportunity to replace 13, the position that Paula had.
"When I became leader and stood for the first time in front of New Zealand, I had Shane just to the right of me; he came in with me in 2014, I rate him highly. I was delighted to be able to put him at 13."
Muller batted away questions over a perceived lack of policies.
"It's not that nothing has come out, I've made a number of announcements - particularly in terms of supporting business to get them back up on their feet ... there's a lot in the can but we're 10 weeks out and I want to make sure we sequence it in the right way. I've got a speech next week which I'm sure you'll be interested in and a number, a series of announcements."
He said the party had a mixture of policies that were complete, and some which were still being worked on.
"A bit of both ... there are certainly some that have been finalised and some that haven't been finalised ... I'm not going to go through that with you on afternoon radio."
"Be assured that we do [have the policies] but we work on our timeframe in terms of when we release it, and I'm sure when we do you'll be delighted to talk to me about it."
Calling for specifics, Checkpoint host Lisa Owen also asked him to clarify his statement earlier in the week about whether people who could prove they were COVID-19 free would be allowed to enter the country without being tested.
"What I was framing up was a criteria that could exist in the future, when clearly that can't happen in the current context... what I was talking about was a critique of the Government's lack of transparency or visibility around what the next step is in terms of opening up our border.
"There's no appetite - from me or any New Zealander - for the border to be open today, partly because of what's happening overseas and partly because of the shemozzle at the border."
Asked what he would do in the Government's position, he said it was more about the medium-term.
"Right now we'd be completely locked up, I'm not suggesting any other change from that ... what does the medium term look like if the pressure reduces in Australia and if they get their Covid situation under control - which clearly they haven't done in Victoria ... is it a COVID test in Australia before you hopped on a plane?
"You have to take your health advice but we have no visibility of what the health advice would look like in the medium term.
"My view - and I assume health experts will get to this point as well, and we'll wait to see - is when you get the pressure low in one country and we're happy with the test regime and the equivalent regime that exists in that country, I assume the advice would be that we would be able to move away from a 14 day two-test regime."