Dan Biggar suffered an ankle sprain in Wales' 16-16 RBS 6 Nations draw with Ireland and will be a doubt for the clash with Scotland.
Wales boss Warren Gatland confirmed the fly-half picked up a "high ankle sprain" in Sunday's match at Dublin's Aviva Stadium, 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 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."
Kiwi-born full-back Anscombe was withdrawn by Wales after suffering a hamstring problem in what head coach Gatland branded a "mature decision".
Now the Cardiff Blues 24-year-old will battle to be fit in time to take on Scotland next weekend.
"Gareth's hamstring was tight on Friday, so we pulled him out of training and Liam ran there all day on Friday," said Gatland. "We made that decision last night that it wasn't worth the risk of starting Gareth, particularly as we didn't have a huge amount of full-back cover.
"It was a decision made as much in conjunction with the medical team and Gareth, it was a mature decision made my Gareth."
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.
"We've worked hard on our scrum in the last 12 months or so, and I thought our scrummaging was outstanding," said Gatland.
"It was one area of the match where we had some real dominance. The front row did a really good job and the guys coming off the bench too.
"With a bit of luck Scotland might agree to have the roof closed and we can go out and both try to play some rugby.
"Unfortunately it's our stadium but we don't have the decision on that, but we'll keep fighting for the rights to do what we want in our own stadium."