Celtic duo Stuart Findlay and Marcus Fraser have been handed their first call-ups to the Scotland U21 squad by interim coach Ricky Sbragia.
The Scots take on Portugal in a challenge match next week and Rangers midfielder Lewis MacLeod and Hearts forward Callum Paterson have also been selected for the first time.
And Chelsea's Islam Feruz, who scored a hat-trick for Sbragia's Scotland U19's in last month's European Championship qualifier against Switzerland, is also in the squad.
Sbragia will be filling in for Billy Stark, who is taking charge of the senior team for their friendly in Luxembourg, following Craig Levein's dismissal.
And Sbragia said: "I am stepping in as U21 coach for one match, so having experience of working with many of the players, and staff, does make the transition easier for all of us.
"Players like Stuart Findlay, Marcus Fraser, Lewis MacLeod, Islam Feruz and Calum Paterson have done very well at U19 level and it is pleasing to see them taking the next step.
"It's an exciting squad. Stuart Findlay has done very well to move through the age groups, Lewis MacLeod is a first-team regular for Rangers, Tony Watt is scoring goals for Celtic, and Islam Feruz is another one to watch.
"Billy selected the squad before going on to work with the senior squad. We have spoken in depth about the plans for this match and it's up to me to carry on Billy's work for now."
Squad: Jordan Archer (Tottenham, on loan at Wycombe), Chris Kettings (Blackpool); Kieran Duffie (Falkirk), Stuart Findlay (Celtic), Marcus Fraser (Celtic), Kevin McHattie (Hearts), Clark Robertson (Aberdeen), Lewis Toshney (Celtic, on loan at Dundee) ; Stuart Armstrong (Dundee United), Fraser Fyvie (Wigan), Jason Holt (Hearts), Kenneth McLean (St Mirren), Lewis MacLeod (Rangers); Islam Feruz (Chelsea), Dylan McGeouch (Celtic), Callum Paterson (Hearts), David Smith (Hearts, on loan at Raith), Anthony Watt (Celtic).