Fly-half Rhys Priestland will not report for Six Nations duty with Wales due to a hamstring injury.
Priestland went off just four minutes into Bath's European Champions Cup defeat against the Scarlets last Friday.
He was named by Wales head coach Warren Gatland in a 39-man Six Nations squad earlier this week, but has now undergone further checks.
In a statement, the Welsh Rugby Union said: "Following further assessments and consultation with a specialist, it has been concluded that due to the severity of Rhys Priestland's hamstring injury, he will remain at Bath Rugby for ongoing rehabilitation and will not link up with the Wales squad on Monday morning.
"It is envisaged that the injury will preclude him from taking an active part for the majority of the Six Nations, hence this course of action has been deemed the most appropriate."
Priestland won his 50th cap during Wales' autumn series earlier this season, but he now becomes their latest injury casualty.
Wales are without Sam Warburton and Jonathan Davies, two stars of the British and Irish Lions' New Zealand tour last summer, for the whole tournament.
Their fellow Lion - Bath No 8 Taulupe Faletau - looks set to be unavailable for Wales' first three Six Nations games against Scotland, England and Ireland while he recovers from a knee injury.
No replacement for Priestland has been summoned by Gatland. His squad contains four other players who can fill the number 10 position in Dan Biggar, Owen Williams, Rhys Patchell and Gareth Anscombe.