Jamie Roberts admits he may not be fit to face Ireland in Wales' Six Nations opener on Sunday, 5 February.
The Cardiff Blues centre suffered a knee injury on 23 December, but was last week named in Wales' training squad ahead of the tournament.
He told the South Wales Echo: "It's touch and go.
"Fingers crossed, I will put myself in the picture to be fully training for that Ireland week and then be able to put myself up for selection."
Blues coaches Gareth Baber and Justin Burnell had hoped Roberts would be fit for their crucial Heineken Cup clash against Racing Metro on Sunday.
But Baber confirmed Roberts's injury is taking more time to clear up than expected.
As he contemplated what lies ahead during Wales' forthcoming training camp in Poland, Roberts said on Twitter: "Tough rehab coming up."
Roberts, a British and Irish Lion, said: "Doctors have said it's hopefully a five-, six-week injury and I'm almost four weeks now.
"Hopefully the rehab will allow me to be fit and fine for that first game. The physios will make that call.
"The rehab is going well. It's feeling all right and it's looking good.
"It's just a ligament strain in the knee. It takes time. Unfortunately, it's one of those things."
Roberts's fellow Blue Gavin Henson is a Wales midfield contender despite coach Warren Gatland admitting the squad's erstwhile celebrity is "underdone" following only three starts since returning from a dislocated wrist.
Scarlets' Jonathan Davies and Scott Williams and rising Ospreys star Ashley Beck are also in the centre mix while Perpignan's James Hook has also worn the Wales 12 jersey.