Williams told British media on Thursday that he told his manager he didn't want to hear anything about negotiations he was having with the Toronto Wolfpack until he was ready.
"My manager was speaking to these guys around the [World Cup], I said I didn't want to hear anything about it as I wouldn't have been doing myself, New Zealand and the All Black jersey any justice.
"I was trying to be the best All Black I could be every single day, [but] as soon as we lost to England…the next day I caught up with my manager and he filled me in…that's when we started having conversations," he said.
Williams then met Wolfpack coach Brian McDermott, a seven time Super League winner as a player and coach, and during a two-hour conversation they 'verbally machine-gunned each other' about whether he would be moving to North America for the right reasons.
Williams then told All Blacks coach Steve Hansen he might be about to return to league.
Originally, Williams said he had intended to play rugby for another year.
But in signing the biggest deal in rugby history worth 10 million pound over two years, he said he understood what he was getting into but as a sportsman it was the sort of environment you wanted to test yourself in.
"It's great what Toronto have done, where they're based and what they're trying to achieve," he said.
McDermott said the club had signed both a brand and a world-class player while Toronto boss Bob Hunter was hopeful Williams could have the same impact as LeBron James and David Beckham.
Williams said he didn't believe he could be compared to either James or Beckham but he was hopeful he could contribute to kickstarting a rugby league revolution in Canada.
"I need to have that purpose, something to believe in and I think I could be really suited to their style of play. We want to turn some heads. It's going to be a journey and there will be pressure, but it's going to be really exciting," he said.
It will be a tough market as ice hockey, football and basketball all have bit support in Toronto.
His contract also has a clause that allows him to retain a right to continue his professional boxing career as well.
The Wolfpack have worked their way through the British league divisions and beat Featherstone Rovers last month to win promotion to Super League. They will start their first season at that level in February.