Steve Clarke says Nathan Patterson is "doubtful" to face Ukraine on 1 June - but is optimistic the right-back will feature at some stage next month.
Patterson made the cut despite fears over his fitness and joins fellow injury doubt Billy Gilmour in the squad.
Kieran Tierney misses out with injury and Clarke confirmed he has known for "weeks" he would't make it.
Scotland face Ukraine before a potential playoff final with Wales on 5 June.
Clarke's team then have a triple header of Nations League games with two clashes with Armenia either side of the trip to face Ireland.
On the injury situation Clarke said: "It's a big blow for everybody just finding out today but we've known for a little while Kieran wouldn't be involved.
"It's disappointing for Kieran and for us.
"At some stage over the four or hopefully five matches, Nathan will be fit to play. His return to play is imminent and it will just come down to match fitness.
"I would put him down as doubtful for the Ukraine game.
"Billy will be fine. Obviously disappointing for someone like Kenny McLean who has missed out again after picking up a broken toe.
"That's disappointing because he's a crucial part of the squad."
The manager also dismissed talk Scotland will be the "bad guys" as they get set to take on Ukraine after the initial November date was postponed due to the harrowing conflict with Russia.
"I don't think it's the first time we've been the bad guys," he said. "We all understand and respect the position of the Ukrainian team.
"Fortunately for them they've managed to get their team out of the country and into a training camp. They've been playing matches and they will be ready for the game.
"We'll be ready too. It's going to be two teams who are ready to go."
