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A two-hour dinner with Toronto Wolfpack coach Brian McDermott in Japan – the week after the All Blacks were knocked out of the tournament in their semifinal defeat to England – and no doubt the staggering offer to play in the English Super League, changed those plans.
Williams met his Manchester-based Wolfpack team-mates for the first time yesterday and today made his first public appearance as the biggest signing in the club's three-year existence.
His big reveal, if you could call it that, involved Williams taking centre stage at Arsenal's Emirates Stadium in north London where his brand and its pulling power was again compared to the likes of LeBron James.
Set against a billboard of Williams featuring in the 2015 World Cup for the All Blacks and the 2013 World Cup semifinal with the Kiwis at Wembley, his introduction alone took five minutes.
Toronto's general manager Martin Vickers listed Williams' two NRL Premierships, 7-0 boxing record, Olympic Games venture with the New Zealand sevens team and that he boasts the most successful win ratio of those to win two Rugby World Cups.
Vickers finished by labelling Williams a pioneer who challenged the boundaries of sport.
Once Williams took his seat, much of the focus centred on how this latest deal – one in which he will reportedly earn $10 million over two years and become the highest paid rugby player on the planet – transpired.
Williams said while he allowed manager Khoder Nasser to negotiate with interested parties during the World Cup, he requested not to be informed until the week after the semifinal defeat.
"My understanding was around the World Cup," Williams said of Toronto's offer which was first reported in February. "That's when I was first made aware of it. Obviously the lads in the teams I've been playing for were giving me stick but I hadn't heard anything from the club.
"My manager was speaking to these guys around that time but I said I don't want to hear anything about it because I wouldn't have done myself, New Zealanders or the jersey any justice thinking that way.
"When we got knocked out after England that's when we started having these conversations.
"It's been a whirlwind. This deal came to fruition in quite a short space of time.
"To be honest before the World Cup I was intending on staying in New Zealand for maybe one more year but once this came about it was an opportunity that I couldn't turn down, and now we're here."
Williams said he began watching Toronto games in Japan to get a feel for their style of play and he then contacted some of their Australian players to gauge feedback. He also recounted how he told All Blacks coach Steve Hansen of his plans.
"It might have been that [final] week on the training paddock Shag as he does comes up to you 'hey how you going cobber is this news right?' I just told him I haven't sat down yet with the coaches but I'm talking to them and if it all goes well it looks like it'll be coming to fruition and I'll be signing."
Other than the obvious financial lure, the dinner where McDermott outlined his vision and the club's ambition after gaining promotion to the Super League ultimately convinced Williams to sign on.
"It was awesome sitting down with Brian it was supposed to be a 30-40 minute catch up and we sat there for over two hours picking each other's brains.
"I loved what he was saying. No disrespect to rugby league but sometimes it can be really monotonous. You know where they are going and where they are going to set up. I really believed in what he was saying.
"I left that meeting thinking not only am I excited about going and playing there but their purpose and what they're trying to achieve as a team."
McDermott made it clear Toronto were keen to leverage Williams' brand as much as possible but that he was more interested in the athlete. He described the dinner as the pair machine gunning each other with questions.
"I think we both knew that night this could be good," McDermott said. "I don't know if it was a done deal from Sonny's point of view but I went out there certainly with the intent that if it didn't go well, Sonny wasn't signing with us.
"The whole night boiled down to one question and that was 'are you coming to be a rugby league player?' On every level that means the good stuff, the headline grabbing stuff but also the hard stuff you've got to go through.
"I don't think it's appropriate to tell you specifically what his answer was but he more than assured me he's there to earn the respect of everyone at the club before he starts being what you think you've signed on.
"My aim is not to get the best from Sonny Bill Williams in round one. His transition from rugby union is going to take some time."
Asked exactly what swung his decision from staying in New Zealand to moving his wife and their young family, including three children and one on the way, to the other side of the world, Williams said he was inspired to pave another pathway in North America.
"For me, yes, I'm a sportsman but I need to have that purpose, something to believe in.
"There's a lot of people that are pointing at us and laughing but if we succeed it will open avenues for young Polynesian and Maori boys, young English lads, that could provide for themselves and their family in another country. That's the way I look at it.
"Overall what they're trying to achieve on and off the field is something special. Instead of looking at the challenges as 'wow, what if I fail?' it's what if we succeed. To say I've been part of that would be something special."
Williams plans to spend five weeks in Sydney for a training camp before shifting north to prepare for his Super League debut against Castleford at Headingly in February.
"When it comes to skill wise and knowing the game I grew up playing the game so I'm confident in that aspect but physically I've got a little bit to go but right here right now I'm in a good space."