Craig Halkett and Ross Stewart have been called up to the Scotland squad for the first time for the upcoming friendly double header.
St Johnstone goalkeeper Zander Clark has replaced QPR number one David Marshall, who has withdrawn along with Nottingham Forest defender Scott McKenna.
Both players suffered hamstring injuries in the Sky Bet Championship game between their teams on Wednesday.
Marshall's QPR team-mate, Lyndon Dykes, is also a fitness doubt for Scotland as the striker has still not played since February 15.
Halkett, the 26-year-old Hearts defender, capped at under-19 level, has been rewarded by national team boss Steve Clarke for an impressive season with the third-placed Tynecastle outfit.
He will have the chance to win his first cap against Poland at Hampden Park on Thursday night or away to either Austria or Wales the following week.
Former St Mirren and Ross County striker Stewart, 25, has scored 22 goals for Sunderland this season and has helped the Black Cats into sixth place in Sky Bet League One.
Injuries to John Souttar and Liam Cooper had left Clarke short of defensive options while Hibernian striker Kevin Nisbet is out long term with a knee problem.
