Matt Phillips, Grant Hanley and James McArthur have pulled out of the Scotland squad ahead of the double-header against Canada and Slovenia, the Scottish FA has confirmed on its Twitter account.
Uncapped Leeds defender Liam Cooper, 25, has been drafted in for the challenge match against the Canadians at Easter Road on Wednesday night and the World Cup qualifier against Slovenia at Hampden Park on Sunday.
Midfielder McArthur missed Crystal Palace’s 1-0 win over Watford at the weekend while defender Grant Hanley played in Newcastle’s goalless draw against Birmingham, with neither player’s injury specified.
Midfielder Phillips missed West Brom’s 3-1 win over Arsenal on Saturday with a hamstring strain and afterwards boss Tony Pulis was quoted as saying midfielder James Morrison will miss the Canada game with an ankle injury picked up in training.
Pulis said: “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.”
The friendly in Edinburgh is a warm-up for the crucial World Cup qualifier. Scotland sit fifth in Group F after picking up four points from their opening four games.
Cooper was born in Hull but qualifies through his Scottish grandfather and has represented Scotland at Under-17 and Under-19 level.
He received his first call-up to the senior Scotland squad in March 2016 for a friendly against Denmark.