Wales full-back Liam Williams could miss the entire NatWest 6 Nations with an abdominal injury.
The 26-year-old suffered a recurrence of the problem playing for Saracens against Ospreys earlier this month.
Head coach Warren Gatland revealed that unless the injury responds to treatment Williams will need an operation, ruling him out of the tournament.
An irritated Gatland also suggested the option of surgery on the problem, which had previously kept Williams out for six weeks, should have been taken up earlier.
"Hopefully they can get him right but if he’s not right he might require surgery," said Gatland.
"He potentially had the option of surgery before, and that was not taken up."
Wales also confirmed that fly-half Dan Biggar will miss the first three matches of the tournament.
The 28-year-old suffered a shoulder injury during Ospreys’ weekend defeat at Clermont Auvergne and will be unavailable for the games against Scotland, England and Ireland.
Wales therefore head into the tournament without their two leading fly-halves as Rhys Priestland is sidelined by a hamstring problem.