The two-time world champion was seen training with his right knee heavily strapped during their final training session in Chiba on Saturday, with former rugby commentator Hamish McKay claiming that an announcement would be made on Sunday afternoon confirming his departure from the squad.
McKay added that Ngani Laumape, the Hurricanes centre, would be called up in his replace, which would have come as the second changed to Steve Hansen's squad in as many days following the loss of forward Luke Jacobsen.
However, the All Blacks have dismissed the reports as incorrect, with a New Zealand Rugy spokesman saying: "The SBW reports are not true."
It's understood that not only is Williams remaining in Japan with the All Blacks, but his family are on their way to Tokyo to support him throughout the campaign that kicks off this weekend.
Williams has been nursing a knock to his right knee, having trained all week with strapping to his leg as well as his right ankle.
But on Sunday he posted an image on Twitter alongside All Blacks teammate Ofa Tu'ungafasi, with the two relaxing on a sofa at the team's Tokyo hotel.
Williams was a part of the successful 2011 and 2015 New Zealand sides, and was of just three players looking to become the first ever triple-World Cup winners alongside captain Kieran Read and lock Sam Whitelock.
The 34-year-old cross-coder has made 53 appearances for the All Blacks, and played a part in all 14 of their World Cup matches across the 2011 and 2015 tournament.
He also became the story of the 2015 final at Twickenham when he gave his winner’s medal to a young boy in the crowd after he ran onto the pitch to hug him.
If Williams is struggling with an injury, Hansen is likely to select Crusaders pair Ryan Crotty and Jack Goodhue in the centre for their opening World Cup match against South Africa on Saturday, with Anton Lienert-Brown the other option in midfield from the existing 31-man squad.
— Sonny Bill Williams (@SonnyBWilliams)
The false reports follow the replacement of back-row forward Luke Jacobsen, who pulled out of the squad on Saturday after being diagnosed with delayed concussion – his third major one in the last two years – with a decision taken to stand him down from the tournament.