'Unsurpassed' Hansen to quit as All Blacks coach as scramble starts for successor

"I think it's right for the team to have someone new after the World Cup, some fresh eyes, some fresh thinking," he told reporters, hinting that his assistant Ian Foster was his preferred successor.

Hansen, a former policeman, took over in late 2011 after working as Graham Henry's assistant for seven years and guided the All Blacks to World Cup victory in 2015.

The team have had a mortgage on rugby's number one ranking under his stewardship, never relinquishing the top spot, and they will seek a third straight world title in Japan next year.

With Hansen in charge, the All Blacks have posted 85 Test victories, eight losses and three draws, a win rate of almost 90 percent. 

"His record is unsurpassed... whatever happens next in Steve's career, his place as a New Zealand rugby legend is guaranteed," New Zealand Rugby chairman Brent Impey said.

While Fred Allen's All Blacks were unbeaten in the 1960s, he was only in charge for 14 Tests. 

Hansen's success rate is unmatched by any All Blacks coach in the professional era, with Henry on 85 percent, John Mitchell 82, John Hart 76 and Wayne Smith 70. 

"Steve Hansen's the best All Blacks coach we've had. He's done a fantastic job," Hart told news website stuff.co.nz.

His departure will start a scramble for his position, with Foster and Ireland's Kiwi-born coach Joe Schmidt considered the frontrunners to replace him.

"I've got opinions but for once in my life I'll keep those opinions to myself because I don't think it's helpful for the process," Hansen said when asked about a successor.

However, he did let slip that Foster "would be a great head coach -- he's developed as a coach and as a man and has some great qualities and his understanding of the game is great".

- 'What's next? I don't know' -

During his tenure, Hansen has displayed a keen eye for talent and instilled a team ethos of constant improvement.

It paid off after 2015, when a string of legendary players including Richie McCaw, Dan Carter, Ma'a Nonu and Conrad Smith retired but the All Blacks' success continued with barely a blip.

Hansen had originally intended to step down in 2017, mid-way through the World Cup cycle, but New Zealand Rugby persuaded him to extend his contract until 2019.

He was adamant that this time, the decision to retire was final, and said he was going to spend more time with his family.

"What's next? I don't know. So don't bother asking," he said, adding that his priority was to guide the All Blacks to victory in Japan, which would be their fourth World Cup victory overall.

Hansen said it would be the fifth World Cup he has attended, and he was still excited at the challenge posed by what will be his final campaign in charge of the team.

"It's probably going to be the toughest World Cup from a competitive point of view," he said.

"The northern hemisphere have really come to the party since the last one and got themselves in good nick. I think Australia and South Africa are capable of winning it if they get their stuff sorted."

Hansen coached domestically with Canterbury and was an assistant at Super Rugby level before moving to Wales in 2001 to work under Henry.

He took over the top job in Cardiff in 2002 but had mixed results before returning to New Zealand two years later to again work as Henry's offsider, this time with the All Blacks.

Henry said his former protege could leave the All Blacks satisfied with his achievements.

"I think he'll feel at peace," he said. "He's been coaching international rugby for nigh on 20 years."