Hamish Watson's involvement at the Rugby World Cup might already be over after he suffered a knee injury in Scotland's 27-3 loss to Ireland.
The flanker was left in pain following a collision with Cian Healy in the first half in Yokohama and faces a nervous wait to discover the results of a scan.
Magnus Bradbury is set to be called into the squad if Edinburgh team-mate Watson is ruled out of the tournament, having travelled to Japan as cover for Jamie Ritchie.
Scotland coach Gregor Townsend admitted the signs are not encouraging for the 27-year-old, who had made an impressive 14 tackles before going down.
"Hamish is our only injury concern," Townsend said at his post-match news conference.
"He had a knee injury that we will hopefully be getting more information on tonight with a scan.
"It doesn't look good when a player is stretchered off the field, so hopefully we'll know more later tonight.
"It would be bad luck for any player if he misses the World Cup. We had Sam Skinner miss out on selection ahead of the World Cup. But we have always presumed that there will be people who will miss the World Cup after each game that we play.
"Let's hope that's not the case with Hamish."
Townsend confirmed fellow flanker Ritchie, 23, would be fit for the country's second Pool A game against Samoa.
Scotland will need all the good news they can get after giving up four tries - including two in the opening 15 minutes - against a far superior Ireland.
Townsend said: "It's disappointing. We didn't start with the energy, accuracy and aggression that is required to beat a team like Ireland. They took their chances well when they got into our 22.
"If you give any team in world rugby a 15 to 20-point start it is going to be very difficult to come back.
"We must play much better in our next three games if we are going to get out of our pool and progress into the quarter-finals and I believe we will be."