This weekend they fell at the final hurdle in a bid to claim successive Guinness PRO14 titles, while also matching their best-ever Champions Cup performance in reaching the semi-finals.
It is a mark of how far this team has come in four seasons under Wayne Pivac that a European semi-final and a domestic final has left the club wondering what might have been.
And yet you only have to go back to 2015 for a time when the Scarlets were on the verge of missing out on the Champions Cup.
That day Benetton led 13-3 with Henry Seniloli on his way to run in their third try, only for Williams to get back and somehow prevent the try.
The Scarlets turned the game around, qualified for Europe and have barely looked back since.
Saturday’s 40-32 defeat to Leinster is a body blow, but even with the departures of Williams, Tadhg Beirne and John Barclay, the team looks well-placed to kick on.
For skipper Ken Owens, injured in last year’s knock-out stages but back up to speed this season, the Scarlets might have been beaten but they are here to stay.
“From where we’ve come four years ago to now, we are at the top table of Europe and in the league,” said Owens.
“People asked whether last year was a fluke but we’ve shown it wasn’t. We’ve shown a lot of character to get back to the final.
“We’ve improved in Europe and got to the semi. As long as we keep pushing ourselves we will be alright.
“It was just small margins that swung in their favour. Wayne said after the game it takes a champion side to beat another champion side.”
A sensational 9️⃣-try thriller unfolded at the Aviva Stadium as Leinster capped off a historic double in the #GUINNESSPRO14FINAL
Catch all the best moments from this classic 🔽 pic.twitter.com/gKlZubQwSE
— PRO14 RUGBY (@PRO14Official) May 27, 2018
Coping with the losses of those three key players will be a challenge, although the Welsh side will be able to call on the likes of Cheetahs duo Clayton Blommetjies and Uzair Cassiem as well as Ospreys centre Kieron Fonotia.
Add in the return to fitness of Jon Davies and Jake Ball and there are reasons to be optimistic for Scarlets fans and for Pivac.
The Scarlets coach said: “The boys have done very well and should be proud of the success they had last year and this year.
“We are not going to sit back and relax and say we have had a pretty good season.
“Now we have to get back to work once we get back into the season and hopefully improve again.”
Whether they can close the gap on Leinster remains to be seen, but with Pivac and Owens leading the way, the Scarlets are a force to be reckoned with for the foreseeable future.