Stephen Kingsley and Hearts goalkeeper Jack Hamilton have been called up by Scotland despite having played five times for their clubs this season.
Hearts' Hamilton, 22, is drafted in for matches against Italy and France, along with Ross County's Scott Fox after Scott Bain and Allan McGregor withdrew.
Swansea City left-back Kingsley, 21, and Derby County midfielder Craig Bryson, 29, are also called up.
That is because club commitments mean four players cannot face Italy.
Scotland face the Italians at the Ta' Qali National Stadium in Malta on 29 May before taking on France in a second friendly on 4 June in Metz.
But Sheffield Wednesday midfielder Barry Bannan and Hull trio Robert Snodgrass, Shaun Maloney and Andrew Robertson are due to play in the English Championship play-off final the day before the game against Italy.
Barring injuries, the quartet are expected to return to the squad before the match in France, but McGregor missed Hull's semi-final win over Derby and is an injury doubt for the final, while Bain also has a back problem.
Hamilton and Kingsley receive their first call-up to Gordon Strachan's senior squad after having been involved previously at under-21 level.
The Hearts goalkeeper, who has had loan spells with Stenhousemuir, Forfar Athletic, East Stirlingshire and East Fife in recent years, has been back-up this season at Tynecastle behind former Scotland goalkeeper Neil Alexander and has only started 10 games for his parent club.
Kingsley, who joined Swansea from Falkirk in 2014, spent the first half of this season with Crewe Alexandra in League One.
The 28-year-old Fox received his first call-up to the senior squad in 2013 but has yet to earn his first cap.
Bryson, who has two senior caps, suffered defeat by Hull with his club in the Championship play-off semi-final.
There could be more changes to Strachan's squad in the coming days, the Scotland coach having rested Celtic and Aberdeen players and offered Hearts the same privilege in recognition of their involvement in the early rounds of European competition next season.
Rangers manager Mark Warburton has hinted he will withdraw left-back Lee Wallace and winger Barrie McKay if his team Saturday's Scottish Cup final against Hibernian.
That would secure an early start to the season in the Europa League qualifiers.
Hibs could re-examine midfielder John McGinn's place in the squad if they claim the trophy.
Scotland squad to face Italy and France
Goalkeepers: Scott Fox (Ross County), Jack Hamilton (Heart of Midlothian), David Marshall (Cardiff City)
Defenders: Christophe Berra (Ipswich Town), Gordon Greer (Brighton and Hove Albion), Grant Hanley (Blackburn Rovers), Alan Hutton (Aston Villa), Russell Martin (Norwich City), Charlie Mulgrew (Celtic), Callum Paterson (Heart of Midlothian), Andrew Robertson (Hull City), Lee Wallace (Rangers)
Midfielders: Ikechi Anya (Watford), Barry Bannan (Sheffield Wednesday), Craig Bryson (Derby County), Oliver Burke (Nottingham Forest), Darren Fletcher (West Bromwich Albion), Shaun Maloney (Hull City), James McArthur (Crystal Palace), John McGinn (Hibernian), Barrie McKay (Rangers), Matt Phillips (Queens Park Rangers), Matt Ritchie (Bournemouth), Robert Snodgrass (Hull City)
Forwards: Steven Fletcher (Sunderland), Chris Martin (Derby County), Ross McCormack (Fulham), Steven Naismith (Norwich City).