Prime Minister Bill English said he was not surprised Murray McCully had decided to move on in 2017 after eight years as Foreign Minister.
McCully announced yesterday that he would not stand for Parliament next year. He had earlier ruled out standing in the East Coast Bays electorate, but said he would stay as long as then Prime Minister John Key wanted him in the Foreign Affairs portfolio.
Asked if McCully had left before he was pushed or if the reshuffle was a factor, English said he was not surprised McCully was going after a "fantastic run".
"There's no doubt the change in leadership has provided an opportunity - well, a catalyst - for people to decide what they are going to do.
"Murray has made a decision and let us know about it."
He said McCully's tenure had included dealing with tough issues on the Security Council over the past two years of New Zealand's membership.
"He's now one of the most experienced foreign ministers in the developed world."
He said he would wait until his reshuffle on Sunday to say whether McCully would stay on as Foreign Minister for a period of time or be replaced immediately.
McCully made the announcement from New York, where he is attending the Security Council and continuing to push for progress on Aleppo.
McCully did not say whether he would stay until the 2017 election.
Erica Stanford was selected as National's candidate in East Coast Bays last month.