Williams joined the Championship club for a four-match spell in January and made his comeback from successive Achilles injuries off the bench away at Moseley.
It may have been an incongruous setting for an All Black but it was a priceless opportunity for Williams to take his first tentative steps back into competitive rugby.
Williams' previous return to action had lasted just three minutes before his right Achilles went again and he arrived at Nottingham with some "mental baggage" to shed.
But he exorcised those demons, finishing his spell at Nottingham with a full 80 minutes against Rotherham before returning home to focus on the Super 15 and then the World Cup.
Williams made his Test comeback for New Zealand in time for the Tri Nations and he is now gearing up for a third World Cup - and the All Blacks' opening clash with Tonga on Friday.
"I owe them (Nottingham) a lot," said Williams, whose parents are both English but emigrated to New Zealand before their 6ft 8in son was born.
"They are a second division side aspiring to get up to the Premiership and it was key in my return.
"They let me do what I needed to do physically and the club rallied around me, there was almost a little fanbase.
"The people there were magic. I still have good memories of that time and I have still got good friends there.
"It was definitely the start of my road to the World Cup. The All Blacks coaches knew about it and agreed with it.
"I owe a lot to them."
Williams is still in touch with Nottingham coach Glenn Delaney, whose links to All Blacks assistant Wayne Smith secured the surprise move.
"Nottingham have been a big club and I am sure they will be again. I will help any way I can," said Williams.
New Zealand are in Pool A with Tonga, Japan, Canada and France, the All Blacks' quarter-final conquerors in 2007.
There have been suggestions Les Bleus could field a weakened team for their clash with the All Blacks, just as Scotland did at the last World Cup.
New Zealand breezed into the quarter-finals in 2007 and then suddenly found themselves up against a battle-hardened French side and lost.
All Blacks coach Graham Henry has learned some valuable lessons from that bitter experience and changed the way his side have prepared for the tournament.
If France do make wholesale changes and Henry feels the All Blacks are not tested enough in the pool stages, he may consider staging a full-blooded internal match.
"At the last World Cup we had a soft qualifying run, we played Scotland B, so I think we need to take those things into consideration," said Henry.
"We might have to work a bit harder during the week. We might have to play 15 against 15 on some occasions in training."
The expectation on the All Blacks to deliver a world title is vast, but the public's excitement is tinged with an air of anxiety.
"You can't worry about it," said captain Richie McCaw.
"The French are traditionally one of the top sides in the world and they will be up for it - but we are looking forward to it.
"A few nerves about the game are good but we back ourselves to train well and come up with the right answers and the right games to win those ones."
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The entire All Blacks apparel line has been updated for 2013/14. Check out the New Zealand All Blacks polo.
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The Gilbert Blitz 8S rugby cleat is a great cleat at a great price of $69.99. Get a new pair of cleats today.
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Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
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The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.