Matt Phillips and James Morrison are both set to miss Scotland's friendly with Canada on Wednesday after missing West Brom's win over Arsenal.
West Brom manager Tony Pulis was quoted as saying Phillips would withdraw from the squad with a hamstring strain.
Midfielder Morrison does still have a chance of making next Sunday's must-win World Cup qualifier at Hampden against Slovenia despite an ankle problem.
Both will meet up with the squad on Monday, when they will be assessed.
Phillips, 26, had returned to the squad for the first time since last summer's friendlies against Italy and France but has missed West Brom's last three matches.