The British and Irish Lions fullback has been struggling with a groin injury.
Wales play England on Saturday, but Williams could return to the national team squad when they visit Ireland on Feb. 24 in their third match of this year's Six Nations.
George North, seeking to prove his fitness after a knee injury, left the Wales squad last week to play for Northampton in Friday’s Anglo-Welsh Cup win over Harlequins, scoring a try and delivering a convincing performance.
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He returned to the Welsh set-up on Monday and 24 hours later was named among the replacements for the clash against England at Twickenham. North was the only change made by Gatland in the matchday 23, after Wales won their Six Nations opener against Scotland 34-7 in Cardiff last week.
(Reporting by Mark Gleeson; Editing by Toby Davis)
