Matt Phillips, James McArthur and Grant Hanley have all withdrawn from the Scotland squad for their upcoming matches against Canada and Slovenia.
Phillips played no part in West Bromwich Albion's 3-1 win over Arsenal on Saturday having picked up a hamstring injury, while fellow Scotland international James Morrison was also absent with an ankle injury.
Manager Tony Pulis confirmed that Morrison would still join up with the squad, though, despite most likely missing the friendly with Canada on Wednesday night.
"Phillips won't be going away with Scotland. Morrison will go, he won't be fit for the first game but there is chance he could be fit for the second game which is the big one," he told reporters.
Uncapped Leeds United defender Liam Cooper has been called into the squad in Hanley's place.