He would cap off a remarkable year if he could also help the Kiwis defend the World Cup, after beating England in their semifinal.
His presence in the Kiwis took them from being a good chance of retaining the title in 2008 to a very good chance, although at no stage have they been considered favourites over Australia.
He scored a first-half hat-trick in a man-of-the-match performance against Papua New Guinea and led the tournament for offloads (13) heading into the semifinals even though he had played only two-and-a-half games (he missed the France game and sat out the second half against Scotland with a neck injury).
It shows why coach Stephen Kearney was right to bring him into the squad at the expense of the unfortunate Tohu Harris after Williams had earlier indicated he would be unavailable.
There doesn't seem to have been any ill-feeling directed at Williams inside the Kiwis camp because they recognise what he could do for their chances. A number of the players have also talked about the example he has set in terms of preparation and professionalism.
"We all knew the ability he had," Kiwis coach Stephen Kearney said. "Seeing him close up like I have over the last four or five weeks, you can see why. To cross three sports, I think you need a bit more than talent. He has an application to his trade and his job which is pretty special.
"He's been a very consistent performer for the Roosters and got them in a position for them to be able to challenge for a premiership. It obviously helped having other talented players there but he had a fairly big impact on the group. It's been wonderful to have him back in the game - and nice to have him part of our side."
Whether he beats Inglis and Brough for the International Player of the Year award will be revealed at a gala awards dinner in Manchester on Thursday morning (NZT).
Inglis was brilliant as he led the Rabbitohs to the cusp of the NRL title, although he struggled a little with a knee injury, and has stood out throughout Australia's World Cup campaign. Brough won the UK Super League's Man of Steel title this year and showed against the Kiwis how good he can be when playing for Scotland.