Williams picked up the problem in Wales’ RBS 6 Nations clash with Ireland in Dublin in February and hasn’t played since.
The 23-year-old, who started the opening two rounds of the 6 Nations alongside Jamie Roberts, had hoped to return in time for the final round of the RaboDirect PRO12 campaign but fell short of that target as he watched his Scarlets side beat Cardiff Blues on Saturday night.
The injury means Williams won’t be available for the Probables versus Possibles trial at the Liberty Stadium on Friday, May 30, or for the two-Test series with the Springboks and the mid-week clash with the Southern Kings next month.
“I wanted to play against the Blues but in the middle of my recovery I had a week where the injury niggled a bit and I couldn’t do much, so that set me back,” said Williams, who hasn’t worn Scarlets colours for four months.
“After that, we decided to leave it for the season and make sure it is 100 per cent for next season in readiness for a big year with the World Cup coming up.
“I am gutted that I am not going to be available, but it is best to make sure it is 100 percent right.
“I had an operation on my other shoulder at the end of last season and it did help me having a full pre-season. I felt I had the best season I have had so far up until the injury.”
Wales defence coach Shaun Edwards has confirmed that Williams won’t be touring as a result of his shoulder worries but he dismissed any suggestions that the midfielder was being rested.
“Scott’s not being rested – he’s injured, that’s why he’s not going. The build up for the Rugby World Cup starts here. It’s not a matter of resting him – I don’t think there’s many people being rested.”
