Scarlets hooker Matthew Rees faces a race against time to be fit for Wales' 6 February Six Nations rugby start against England at Twickenham.
He will be out for at least three months after suffering a groin tear in Saturday's 33-12 loss to Australia.
Wales and the Scarlets say the extent of Rees' injury is unknown.
Scarlets senior medical officer Mark Ridgewell said: "I would not expect him to be available for at least the next 12 weeks."
Wales physiotherapist Mark Davies added: "It is fair to say there is a strong likelihood that he will be requiring surgery and we will know more once that surgery has been undertaken."
Scarlets boss Nigel Davies said: Scarlets Head Coach Nigel Davies said: "The injury will rule him out for a while but we have belief in the strength and depth of the squad this season.
I like to take people on and run from my own line and, if England do not agree with that style of rugby, I am not their man." England may not be playing well, but their two home matches in next year's Six Nations hospitalityare already sell-outs and all the hospitality for the first game, against Wales in February, have been taken. Australia and New Zealand are not so fortunate commercially and they will express their concerns about the stagnancy of the game on the field at this weekend's gathering of the International Rugby Board's general assembly in Dublin, followed by a meeting of the council.
"As I have said already, it is frustrating for us to have key players side-lined, but it's rugby - we will pick up injuries and we have to be realistic and pragmatic about that."
Rees joined Ospreys wing Shane Williams and Cardiff Blues wing Leigh Halfpenny in being injured against the Wallabies and was replaced by Osprey Huw Bennett.
British and Irish Lion Rees joined fellow Scarlets flanker Dafydd Jones (shoulder) and wing Mark Jones in suffering injuries while on Wales duty.
Scarlets skipper Mark Jones damaged a knee in training ahead of the November opener against New Zealand, the 19-12 defeat in which his flanker namesake was injured.
Mark and Dafydd are not expected to return to action until early February, ruling them out of contention for Wales v England rubgy at Twickenham on 6 February.
Back-three player Morgan Stoddart is also out of action until mid-December due to a hamstring strain suffered training with Wales as wing Jones' replacement.
Williams damaged a hamstring and Halfpenny suffered a dead leg in Wales' 33-12 defeat by Australia.
Williams will be out for up to six weeks but Halfpenny is expected to fit for selection for the Blues' clash against Connacht at Cardiff City Stadium on Sunday.
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