Williams, who can play at fullback or on the wing and was a stand-out performer for the British & Irish Lions in their drawn series with the All Blacks in June, was injured in the 13-6 win over Georgia last weekend.
He is joined on the sidelines by wing Alex Cuthbert, who injured his calf, leaving coach Warren Gatland short on options in his back three.
“No time frame for recovery has been set for either player. They have been released back to their respective club/region," a statement from the Welsh Rugby Union said.
Wales defence coach Shaun Edwards said the absence of the pair offered an opportunity to others to step up.
“The next guy on the roster is up. I think Steff (Evans) and Hallam (Amos) have got a pretty good chance of getting picked. We’ll work it out,” Edwards told reporters on Tuesday.
“We’ve gone from having the biggest backline in world rugby to one of the smallest.”
Amos endured a difficult tour of New Zealand with Wales in 2016, starting all three defeats. Edwards believes he is an improved performer this year.
“If I was Hallam Amos, I’d be wanting to show how much I’ve improved since then,” Edwards said. “Hopefully this time he’ll show the All Blacks that his concentration levels and tactical understanding have improved. It’s exciting times for him.”
Even if fit, Saracens’ Williams will miss Wales’s final match of 2017 against South Africa in Cardiff on Dec. 2 as the match falls outside of the international window.
(Reporting By Nick Said; editing by Clare Fallon)
