Dan Biggar suffered an ankle sprain in Wales' 16-16 Six Nations draw with Ireland and will be a doubt for the clash with Scotland.
Wales boss Warren Gatland confirmed the five-eighth picked up a "high ankle sprain" in Sunday's match in Dublin, and suggested Biggar could undergo scans to determine the extent of the problem.
Wales will host Scotland at the Millennium Stadium on Saturday, with Gatland hoping New Zealand-born fullback Gareth Anscombe can be available after the tight hamstring that kept him out of the Ireland tie.
"Dan has a high ankle sprain, so we'll know more on that in the next 24 to 48 hours," said Gatland. "Whether he's got to be scanned or not I don't know.
"It's difficult to make assessments so soon after the game.
"I thought Rhys Priestland played well when he came on and we were happy with his performance."
Gatland was "not satisfied at all" with the draw in Dublin, while captain Sam Warburton insisted Wales' three home matches are now "must-win" contests.
"Even after we lost Dan (Biggar) it didn't really faze us too much, with Rhys coming on and doing well," said Warburton.
"We have got three home games out of four now, and they are must-win matches.
"There was no chance we would have underestimated Ireland. Ireland are always one of the toughest international sides.
"It's one of the toughest games you're going to play in. No Welshman will ever underestimate Ireland."
Gatland has challenged Wales to produce a stronger start when facing Vern Cotter's Scotland next weekend.
"We're not satisfied with the result at all," said Gatland.
"I think on reflection we didn't start well for the first 20 minutes, but then got ourselves back into the game, dominated territory and possession.
"We possibly should have come away with the win, but I won't take anything away from Ireland and maybe the draw was a fair reflection."
Hailing Wales' scrummaging performance, where rookie prop Rob Evans excelled and justified his selection, Gatland admitted he hopes Scotland will agree to have the Millennium Stadium roof closed next weekend.
Both teams need to agree for the roof to be closed in Cardiff, and Gatland hopes Scotland will acquiesce in order to produce some running rugby, with wind and rain likely in the Welsh capital.
