Rhys Williams is battling to be fit for Wales' Grand Slam bid against Ireland at the Millennium Stadium on Saturday.
The Cardiff Blues' wing, who scored two tries in the record-breaking RBS 6 Nations Championship victory over Scotland last Sunday, has aggravated a calf muscle injury.
Wales coach Mike Ruddock has decided to delay his team announcement until Wednesday lunch time, as checks are carried out on Williams, his fellow wing, Hal Luscombe, hooker Mefin Davies and squad scrum-half Gareth Cooper.
If Williams and Luscombe, who was on the bench in Edinburgh, both fail to make it, then Ruddock might have to go outside his current group of players to find an alternative.
"Rhys aggravated a calf injury," said Wales team physiotherapist Mark Davies.
"It is an injury that we are applying ourselves to, and we are keeping our fingers crossed. There is a good deal of uncertainty about his fitness."
Luscombe is nursing a hamstring problem, while Davies is suffering from a knock to his leg and is not training at the moment as a precaution.
Cooper, meanwhile, missed out on the Scotland game due to an ankle injury during the IRB Tsunami Aid match at Twickenham earlier this month, and is unlikely to recover in time for this weekend, so Mike Phillips is set to continue on the bench as Dwayne Peel's understudy.
"The players are battered and bruised, and there is a short turn around from last Sunday to the Ireland game," added Davies.