Wales fly-half Sam Costelow is expected to be sidelined until January after suffering shoulder and hamstring injuries.
Scarlets playmaker Costelow was hurt during Wales’ 49-26 victory over the Barbarians on Saturday and went off at half-time.
He is a clear favourite to succeed Dan Biggar, who retired from Test rugby after the World Cup, in Wales’ number 10 shirt.
Wales kick off their Six Nations campaign against Scotland in Cardiff on February 3.
“We are not expecting him in the short term,” Scarlets head coach Dwayne Peel told reporters ahead of Saturday’s United Rugby Championship clash against South African side the Lions.
“It will be beyond Christmas, beyond the new year before we see him. I haven’t an exact date. We are still waiting on the final prognosis and some specialist opinion, really, on that.
“It is a disappointing one for us because he is going to be out for the large part of the first half of the season.
“There is loads more to come from him, and this is obviously a setback in his career at the minute to have this injury.”
Costelow impressed for Wales at the World Cup in France, starting the pool game against Georgia when Gareth Anscombe was a late withdrawal.
And he is the latest member of that squad to be sidelined, with Exeter forward Christ Tshiunza suffering a broken foot on his return to domestic action and number eight Taulupe Faletau continuing his recovery from a broken arm sustained in the Georgia match.
Wales, meanwhile, are without the Six Nations services of Anscombe and full-back Liam Williams, who will play domestic rugby in Japan next year.