Scotland captain Andy Robertson and Lyndon Dykes have not joined up with the squad ahead of Thursday’s friendly with Poland.
The Liverpool left-back, who missed the FA Cup tie against Nottingham Forest at the weekend, has Covid-19.
Striker Dykes has missed the last six games for QPR with a hamstring injury and is being assessed by his club.
After Steve Clarke’s host Poland at Hampden, they are away to either Wales or Austria next week.
Scotland coach Steven Naismith said: “There is hope that they will be back involved at some point, when that is will be determined by the clubs and the protocols that are in place but there is hope that they will join the squad at some point.
“But in terms of the first game, it is pretty clear that the group who are here will be the ones that we focus on for this game.
“Then as with every game, we will look at the injuries and things like that after that.
“It is a day-by-day situation, Robbo has Covid so there is a protocol you have to follow and Lyndon is back at his club getting treatment and seeing where he is so there is constant dialogue day-to day but there is a hope that they will be involved at some stage.
“Tomorrow might change in terms of circumstances but again the clubs are the ones who will drive the situation because they will not release a player when they have an injury or when they are not right.”