Wales are in danger of losing the services of Dan Lydiate for possibly the entire Six Nations tournament after the flanker sustained a bicep injury.
The 30-year-old sustained the blow while playing for his club Ospreys in the 24th minute of the Pro 14 game against Dragons on Sunday.
"It could be a tendon in the bicep. It's not looking too great," Ospreys defence coach Brad Davis told Ospreys TV.
"You try to look at the best-case scenarios, six-eight weeks, but worst-case scenario, they have got to operate.
"We will know a lot more about that once he has a scan and the medics can plan the way forward."
Wales are already without Sam Warburton while number eight Taulupe Faletau is recovering from a knee injury. Ross Moriarty's participation is also clouded with an injury concern. Meanwhile, Jonathan Davies is another long-term absentee, having been hurt during Wales' November defeat against Australia.
Wales open their Six Nations' campaign against Scotland at Principality Stadium on 3rd February.