Matt Phillips, James McArthur and Grant Hanley will miss Scotland's double header with Canada and Slovenia after withdrawing from the Scotland squad.
Leeds United defender Liam Cooper has been called up as a replacement.
West Brom's James Morrison is also a doubt for Wednesday's friendly with Canada after missing his side's win over Arsenal.
Midfielder Morrison could still make the World Cup qualifier at Hampden against Slovenia on 26 March.
West Brom manager Tony Pulis was quoted as saying Phillips would withdraw from the squad with a hamstring strain.
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 past three matches.