Wales international Dan Lydiate looks set to miss at least part of this season's Six Nations after suffering a bicep injury.
Lydiate was hurt during the Ospreys' PRO14 victory over the Dragons on New Year's Eve.
"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."
Lydiate appears unlikely to be available for Wales' opening three games against Scotland, England and Ireland, but he could potentially miss the whole tournament, which starts on February 3.
Wales are already without Lydiate's fellow flanker Sam Warburton for the competition due to injury, while No.8 Taulupe Faletau is recovering from knee trouble and thought unlikely to be back in action until late February or early March. Back-rower Ross Moriarty is also sidelined through injury.
Centre Jonathan Davies, meanwhile, is another long-term absentee, having been hurt during Wales' November defeat to Australia.
Although 62-match veteran Lydiate started only one Test for Wales in 2017, he remains an integral squad member and captained his country against Georgia six weeks ago.