The 30-year-old was due to be back in contention to face Munster this weekend, but suffered appendicitis which required surgery.
It means he will also be unavailable for the Scarlets’ October fixtures against Leinster and Cell C Sharks.
Wales face New Zealand at the Principality Stadium on October 30 and should Williams fail to recover in time, head coach Wayne Pivac could look draw on the impressive strength in depth within Welsh rugby with Cardiff’s Hallam Amos and the Scarlets’ Johnny McNicholl in good form.
“He’s okay, he’s back in the club, but it’s just unfortunate timing for him and for us but he’ll be out for the period,” said Scarlets head coach Dwayne Peel of Williams.
“I’m unclear yet but I can’t imagine he’d play for us in these block of games.”
