Scotland have added Murray Davidson and Darren Barr to their squad for Wednesday's friendly match against Luxembourg.
St Johnstone midfielder Davidson joins a trio of new caps - Leigh Griffiths, Andrew Shinnie and Liam Kelly - who were added to Billy Stark's travelling party on Sunday.
Davidson has been in previous squads for games against the Faroe Islands and Brazil but has yet to make his international debut.
"I'm delighted," Davidson told his club's official website. "I've been involved before and got on the bench both times.
"But I've been out of the scene for a wee while now so it's great to be given this chance."
Hearts defender Barr has also been added to the squad and could win his second Scotland cap following his 2008 debut against Northern Ireland.
The call-ups follow the addition of Hibernian striker Griffiths, Inverness midfielder Shinnie and Kilmarnock playmaker Kelly to Stark's travelling party.
Scotland U21 coach Stark, who is in temporarty charge following the departure of Craig Levein, sent for the trio after nine players pulled out of his initial squad.
"At this stage of the season - with weekend and midweek games - niggles, strains and withdrawals are to be expected," he said.
"But it gives us a chance to have a look at players who may not have have international experience but are in tremendous form for their clubs."