Wales are waiting on the fitness of Jamie Roberts, Rhys Priestland and Dan Lydiate ahead of their opening Six Nations match away to Ireland in Dublin on Sunday.
Newport flank Lydiate has an ankle problem while Cardiff centre Roberts and Scarlets flyhalf Priestland, one of the success stories in Wales's run to the semifinals of last year's World Cup, are both struggling with knee injuries.
All three took some part in last week's training camp in Poland and Wales have delayed naming their team for the Lansdowne Road clash until Friday in order to give the trio the best chance possible of playing this weekend.
"Last week went well, obviously with Dan Lydiate and Rhys Priestland we are still waiting," Wales assistant coach Rob Howley said on Tuesday.
"In terms of their participation, it was very limited last week. Dan and Rhys probably did about two or three sessions but they were just limited to skills, the next 48 hours is pretty critical and we are waiting to see how they are.
"They have come in this morning and they are a little bit sore after the weekend's endeavours but we are obviously hopeful," the former Wales and British and Irish Lions scrumhalf added.
"Jamie participated a little bit more than Dan and Rhys but we are still uncertain. Jamie has not played for a long time, I think it's around five or six weeks, so we are, once again, waiting to see how the next 48 hours goes," said Howley.
If Priestland is ruled out then James Hook, as happened at the World Cup, could start at flyhalf with either Stephen Jones or Gavin Henson on the bench.
Henson could also come in at centre if Roberts remains unfit.
Meanwhile former captain Ryan Jones and Andy Powell are possible back-row replacements for Lydiate.
Wales - who beat the Irish in the World Cup quarterfinals - are already without prop Gethin Jenkins and first-choice locks Alun Wyn Jones and Luke Charteris.
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