Leicester Tigers director of rugby Richard Cockerill has ruled out signing any "journeymen" to increase squad numbers for next season.
"The reality is, the reserves in key positions will play a lot of rugby.
"You have to cover all your bases. These second and third choice players have to be good; they can't just be journeymen to fill the squad," Cockerill told BBC Radio Leicester.
"We need guys who can play top end, both in Premiership and European rugby."
Leicester announced in January that fly-half George Ford would be joining Bath in the summer and they have replaced him by signing both Williams and Northampton number 10 Ryan Lamb to play at Welford Road next season.
"Owen is a very, very good goal-kicker and with George Ford moving on we wanted to get another young player in there to develop and bring through," Cockerill continued.
"He'll get lots of opportunity and its there for him to take that and push his claims to hopefully become a very good player.
"Obviously Scarlets are disappointed Owen has left, as we are when guys like Billy Twelvetrees and George Ford leave. Unfortunately ,that's the way of the world and we just have to get on with it."