Cardiff Blues and Wales back Gareth Anscombe has been ruled out for at least two months with an ankle injury.
Anscombe, 24, will have surgery after sustaining the injury during Wales' World Cup quarter-final defeat to South Africa.
He could now be a doubt for Wales' 2016 Six Nations campaign.
"Depending on the severity it'll probably be the other side of Christmas but I can't confirm that yet," said Blues head coach Danny Wilson.
New Zealand-born Anscombe, who qualifies to play for Wales through his mother, joined the Blues from Waikato Chiefs in New Zealand in July 2014.
He made 17 appearances for the Welsh side last season but has not featured yet in this campaign because of his international commitments.
Anscombe, who can play at fly-half or full-back, was ruled out of Wales' initial 31-man World Cup squad with a similar injury.
Having missed the start of the tournament, he started at full-back against Australia and South Africa as Wales were knocked out at the quarter-final stage.
United States forward Cam Dolan will be the Blues' only World Cup player involved away against Ulster in the Pro12 on Friday.
Wales scrum-half Lloyd Williams is likely to feature the following week against Zebre, along with Samoa centre Ray Lee-Lo and USA full-back or wing Blaine Scully.
The other Wales players, Sam Warburton, Gethin Jenkins, and Alex Cuthbert, will be assessed but are set to be given a more extended break.
Meanwhile, 20-year-old utility back Aled Summerhill, who can play full-back, wing or centre, has been given a new two-year contract.
Summerhill has played for Wales sevens and was among the players providing training opposition for Wales during World Cup preparations.