Liam Williams: Lions back adds to Wales injury concerns
Back Liam Williams is a doubt for Wales' Six Nations opener against Scotland on 3 February.
Williams has an abdominal injury which Wales head coach Warren Gatland says might require surgery if it does not respond to treatment and potentially rule him out of the tournament.
"He is being rehabbed extensively over the next couple of weeks," said Gatland.
"Hopefully they can get him right but if he's not, he might require surgery."
Williams was injured playing for Wales against Georgia in November, and missed six weeks before playing for Saracens in the 15-15 draw with Ospreys in the European Champions Cup.
Gatland suggested the option of surgery on the problem could have been taken up earlier.
"It's probably an injury that six weeks ago he should have had an operation on it, but Saracens had rehabbed him and he's come away from the game against the Ospreys feeling very sore," added Gatland.
"Potentially he had the option of having surgery before but that wasn't taken.
"Our medical team had a look and want to rehab him extensively over next couple of weeks."
The news adds to Wales' lengthy injury concerns, with first-choice fly-half Dan Biggar set to miss the first three rounds.
The Ospreys 10 injured a shoulder in last weekend's European Champions Cup loss to Clermont Auvergne.
Fellow fly-half Rhys Priestland Rhys Priestland is also out of most of the tournament with a hamstring problem.
Head coach Warren Gatland was already without Lions back-rows Sam Warburton and Taulupe Faletau, plus centre Jonathan Davies, while wing George North and Gloucester flanker Ross Moriarty have only just returned from injury.
Dragons wing Hallam Amos suffered an ankle injury in the Christmas derby match against Cardiff Blues and has also only just returned to playing.
Another Lion, Ospreys back-row Dan Lydiate, has been ruled out for the season, while Scarlets lock Jake Ball (shoulder) is another player likely to miss the whole of the tournament.