The 35-year-old Cardiff Blues flanker needs just two more Test match appearances to join his fellow former Wales captain Gareth Thomas as only the second Welsh cap centurion.
But Wales coach Warren Gatland has allowed no room for sentiment in his 28-man squad for this season’s RBS 6 Nations Championship, which begins when England arrive at the Millennium Stadium on February 4.
Williams, a three-time British and Irish Lions tourist, misses out as Gatland has opted for more youthful openside options in the form of Williams’ Blues colleague Sam Warburton and Scarlets’ highly-rated Josh Turnbull.
Gatland’s group includes five uncapped players in Turnbull, Scarlets back Rhys Priestland, front-row forwards Ryan Bevington and Scott Andrews, plus back-row prospect Toby Faletau.
Williams is not the only player to be squeezed out, with the likes of Dan Biggar, Tom James, Aled Brew, Tom Prydie, Huw Bennett and Ian Gough also deemed surplus to requirements.
Gatland additionally has to contend with a lengthy injury list, as absentees include props Gethin Jenkins and Adam Jones, centre Tom Shanklin and wing George North, while scrum-half Richie Rees is banned until late March.
But three fit-again Lions – Shane Williams, Leigh Halfpenny and Jamie Roberts – are back, together with experienced Sale Sharks scrum-half Dwayne Peel.
Shane Williams, Wales’ record try-scorer, dislocated his shoulder during the defeat against world champions South Africa in November, but made an impressive return for the Ospreys in their Heineken Cup victory over Toulon on Saturday.
Scarlets hooker Matthew Rees has retained the captaincy of a squad that Gatland hopes can make its presence felt in this season’s Six Nations.
Gatland said: “We have deliberately kept the squad as small as possible and have reverted back largely to the philosophy we had during the Grand Slam year in 2008.
“We want to keep intensity levels up in training and have ensured that we are not carrying players with injury.
“Everyone here is fighting fit and able to take a full part and challenge each other for selection.
“Up front, it’s well documented that we have lost a couple of players in the front row, but that gives opportunities to others to put their hands up, and we are pleased with the options we have got in the pack.
“The forwards have been going pretty well, and we have decided to give a couple of youngsters a chance in this tournament, but that doesn’t mean there is no way back for those who have missed out.
“We are conscious that we need now to begin to realise our potential, and that means winning some games.
“It all starts against England at the Millennium Stadium in a fortnight, and they don’t come much bigger than that.”