Three more years to hone his craft. Three more years to cement his place at second five-eighth. And three more years to leave a lasting legacy in the XV-man code. You can be sure the best is yet to come from Sonny Bill Williams.

Fruitful doesn't begin to describe the benefits of Williams committing his long-term future to New Zealand rugby. His prized signature is another victory for player retention at the top echelon of the game here.

We've seen previously what Williams can achieve in short stints. Imagine how good his intrinsic skills and freakish athletic talent can become with his focus locked on one code for the majority of each season.

PHIL WALTER/GETTY IMAGES From left, NZR CEO Steve Tew, Sonny Bill Williams and All Black coach Steve Hansen during Friday's press conference.

"I've only played rugby on one-year or two-year deals. At this stage right now I feel I took my game to another level at the World Cup. Working alongside Steve Hansen, Ian Foster and Wayne Smith it got a lot out of me. I want to see where I can take my game in the next three years so that's why," Williams said of his choice to break the mould of one-year agreements.

"I love winning and I love the challenge."

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Included in Williams' new deal is the provision for him to box or jump in the sevens arena during the off-season. Both, he feels, allow him to rejuvenate mentally and get his body in the best possible shape.

Outside those small stints, though, his single drive will be on the Blues and All Blacks, after pursuing the Rio Olympic dream with the sevens team.

Based in particular on his influential performances off the bench in the opening pool match against Argentina at Wembley and in the final triumph over Australia at Twickenham, few would argue with Williams' assessment of his own game.

Elevation to the All Blacks leadership group this year further opened his eyes to the significance the national team holds. And with Ma'a Nonu moving on to France, Williams has his eyes firmly set on making the No 12 jersey his own.

That's the one thing to elude Williams in his illustrious career; a regular starting role in the All Blacks. Now is his chance to tick that box, too.

"I grew up as a league boy I'm not going to lie I always wanted to play for the Kiwis. But now this is where my path is and it's an amazing feeling to be part of such a high quality team.

"I must admit when I first came back I didn't really know too much about what it means to be an All Black. Now I do. I consider myself a rugby player and I just love the environment.

"Just coming back in here this morning I got those goose bumps. It's such a demanding team but I really enjoy that."

One call from Steve Hansen after the World Cup was all it took to convince Williams the black jersey remained his biggest burning desire. He's played 33 tests since his debut in 2010 - and has now given himself plenty of time to reach the half-century milestone he craves.

"When you have probably the best coach ever in the XV-man game telling you you're part of his plans that really means a lot. Straight after that call I pretty much got onto my manager and said this is where I want to stay. It was a clear-cut decision I wanted to stay. I said 'let's get the contract done'."

That didn't stop offers rolling in from the NRL, where the Sydney Roosters were keen to lure him back, and persistent French clubs.

"There were European clubs come in with offers. I didn't want to lead them on but some of them wouldn't take no for an answer. It's flattering and as a sportsman it's always good to have those options but I'm very happy with this deal."

If the decision to remain in New Zealand was an easy one, the choice between the Blues and Chiefs was anything but.

Williams helped the Chiefs claim their maiden title in 2012. He feels a strong degree of loyalty towards the Hamilton-based franchise, to the point he made it clear he considers himself a "Chiefs man" until next year.

His sense of guilt at signing with the Blues was obvious. Tana Umaga was a trump card, but Williams said being close to his mum and extended family in Auckland allowed them to support wife, Alana, and daughter, Imaan.

"I'd like to say to the Chiefs I had a couple of really great years down there. Thank you to Dave Rennie and everyone. It was a really hard decision to turn my back on them. Especially with the opportunity to play outside Aaron Cruden and alongside guys like Sam Cane.

"It wasn't an easy decision but I've got a young family; a little daughter and hopefully we'll have some more kids running round in the next few years. My wife doesn't have any family here and most of my family is in Auckland. I'm an Auckland kid so this is pretty much home to me as well.

"We travel a lot and my wife needs a bit of support. That weighed a lot in my decision and it's no secret me and Tana go way back."