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Williams hurt his right knee when providing the offload for Otere Black's try against the Stormers at Eden Park, a problem which kept him from the win over the Waratahs last weekend.
After it was decided that arthroscopy surgery was necessary in order to tidy up a cartilage issue which has been troubling the big midfielder for some time, he must now get used to a much longer break and the clock is ticking on his All Blacks ambitions this year.
He will not make the All Blacks foundation day in Wellington on Monday, but no player has been called into the initial squad of 41 as a replacement.
"It's a big blow," Blues coach Leon MacDonald said today.
"I feel sorry for him. It's unfortunate, he's obviously landed on it awkwardly and has caused some damage there. For him to have a return-to-rugby plan will help. We'll miss him on the rugby field, obviously, but he's still contributing in the meeting rooms and where he can."
Asked about his future in terms of the rest of the season and beyond for the All Blacks, who play their first World Cup match against South Africa in Yokohama in five months, MacDonald sounded cautiously optimistic.
"Whatever he puts his mind to, he makes happen," he said. "If he still wants to play later on he's the sort of guy you'd never write off. This year he really wants to make the World Cup squad and be a part of that obviously, so he's driven to recover well from this injury and get back on the field."
Williams' absence puts more importance on Ma'a Nonu, the second-five who has gone to a new level recently as the Blues have strung four wins together in a season for the first time since 2011.
"We're lucky to have Ma'a and he's thriving with the extra minutes and game time," MacDonald said.
Williams' latest issue comes on top of ankle, wrist and shoulder problems over the past few years.
He is a rare talent but his confrontational style in both union and league has taken its toll and the best he can probably hope for is one last hurrah.
He is contracted to the Blues and New Zealand Rugby until the end of the year, and it's difficult to see him re-committing given that injury toll and what he has achieved.
Over the next seven weeks, the Blues play the Chiefs and Highlanders before having a bye. Then they play the Brumbies, Hurricanes, Chiefs again and the Crusaders.