Wales coach Warren Gatland says fly-half Owen Williams only earned a recall for the 2023 Six Nations by impressing in recent games.
The 30-year-old is at Ospreys as injury cover for Gareth Anscombe and impressed Gatland in his latest encounters against Leinster and Montpellier.
"It was an easy decision for us," said Gatland.
He also explained the reasons for Osprey Rhys Webb's return at the age of 34.
"The nines that we've picked are probably our best kicking nines," said Gatland of Webb, Tomos Williams and Kieran Hardy.
"In this competition you need nines, particularly with your box kicking, to be on the money and on the mark. Rhys will come in and put pressure on those other two nines which I see as a positive with his experience.
"He's been playing well, but definitely the kicking of those three nines we've picked is something that's pretty important in this competition."
Williams last played for Wales - under Gatland - in November 2017 and joined Ospreys on a short-term deal following the demise of English Premiership side Worcester.
He has been a steadying influence as Ospreys turned around their United Rugby Championship (URC) form to beat French champions Montpellier home and away while also making a point against leading Irish province Leinster.
Gatland had previously toyed with using Williams at inside centre, but said: "I haven't picked him as a 12, just as a 10.
"I thought Saturday night's game between Ospreys and Montpellier was a proper game.
"That's where you want your regional teams to be playing, at that level and competing at that level all the time.
"I thought the previous week against Leinster they were a little bit unlucky and probably stopped a little bit of line-speed defensively, but they put themselves in a position to beat Leinster which was encouraging.
"To be honest before that he wasn't in consideration, but it was an outstanding performance he gave at 10, and given his experience I don't think we could ignore that especially given the way the team played, and the way he controlled the game."