Ospreys forwards Nicky Smith and Dan Lydiate are injury doubts for the start of Wales' Six Nations campaign.
Regional head coach Allen Clarke confirmed Smith and Lydiate will be out for between four to six weeks.
Wales begin the Six Nations against France in Paris on Friday, 1 February.
Back-row Lydiate has suffered a recurrence of an elbow injury, while loose-head prop Smith suffered an ankle injury in Ospreys' 51-20 win over Stade Francais on 8 December.
Lydiate's elbow problem forced him out of Wales' side to face South Africa on 24 November after initially being selected.
"They are long-termers so they won't be in the picture for a few weeks yet," Clarke said.
"They will be out for a minimum of four to six weeks.
"Dan has suffered a recurrence of an injury on his bicep so they are looking at that."
The pair's potential absence is further bad news for Wales coach Warren Gatland.
Scarlets announced last week fly-half Rhys Patchell (hamstring) and second-row Jake Ball (shoulder) could both be out for up to six weeks.
Wales and Scarlets full-back Leigh Halfpenny has not played in eight weeks since suffering concussion against Australia on 10 November.
Saracens wing Liam Williams has not played since Wales' win over the Springboks because of a hamstring problem, although the British and Irish Lion is expected back in early January.
Wales back-row Taulupe Faletau has been sidelined since October with a broken arm and is expected back in the first two weeks of January for Bath.