Wales captain Jac Morgan is in danger of missing the 2024 Six Nations after Ospreys confirmed the flanker has had knee surgery.
Ospreys head coach Toby Booth admitted Morgan being fit for the tournament “would be difficult” and said Morgan would be out for “months not weeks”.
Wales’ opening game is against Scotland on 3 February in Cardiff before the finale against Italy on 16 March.
Head coach Warren Gatland names his squad in mid-January.
“The operation was a success and the right thing to do and it needed to be done,” said Booth.
“He is a young man who heals quickly but the certainty about being a professional player is you know you are going to spend time injured and that resilience will be tested.
“We will look forward to getting him better off the pitch so when he comes back, which will be months not weeks, he will hit the ground running.”
Morgan and Dewi Lake were named as co-captains for the World Cup before Morgan was given the role for the uncapped match against Barbarians in November.
Lake, Adam Beard and Will Rowlands will be contenders to be named as skipper for the Six Nations, while lock Dafydd Jenkins has been leading Exeter.
Gatland already has back-row fitness concerns, with Cardiff number eight Taulupe Faletau recovering from a broken arm suffered in the World Cup pool victory against Georgia with a return date in January 2024 initially pencilled in.
“He’s fine,” said Cardiff head coach Matt Sherratt.
“I spoke to him yesterday, he said his arm is feeling pretty good.
“It’s healing well. He’s started running, just to try and get his load up. I think it’s all going as planned.
“There’s no return date, but he’s happy with how he’s travelling.”
Exeter’s Christ Tshiunza is currently sidelined with a broken foot, while Scarlets flanker Taine Plumtree is set to miss the Six Nations after having shoulder surgery.