Scotland have called up Fulham striker Ross McCormack and Birmingham right-back Paul Caddis for Thursday's friendly against the Czech Republic.
Norwich duo Steven Naismith and Steven Whittaker have both withdrawn from the squad preparing for the trip to Prague.
Naismith has a hamstring injury while Whittaker's wife is due to give birth.
Caddis' call-up brings the number of uncapped players in the two squads to face the Czechs and Denmark - at Hampden Park on 29 March - to eight.
Hibernian midfielder John McGinn, Celtic left-back Kieran Tierney, Aberdeen midfielder Kenny McLean, on-loan Blackburn striker Tony Watt, Nottingham Forest midfielder Oliver Burke, Brighton's Jamie Murphy and Leeds defender Liam Cooper are the other players yet to taste senior international football.
Manager Gordon Strachan will use the games to assess some new faces ahead of the 2018 World Cup qualifiers.
The Danish squad includes Celtic defender Erik Sviatchenko, Leicester keeper Kasper Schmeichel, former Liverpool centre-back Daniel Agger and Tottenham midfielder Christian Eriksen.
Scotland squad to face Czech Republic on 24 March
Scott Bain (Dundee), Allan McGregor (Hull)
Christophe Berra (Ipswich), Gordon Greer (Brighton), Alan Hutton (Aston Villa), Russell Martin (Norwich), Charlie Mulgrew (Celtic), Andrew Robertson (Hull), Paul Caddis (Birmingham)
Ikechi Anya (Watford), Barry Bannan (Sheffield Wednesday), Darren Fletcher (West Brom), Kevin McDonald (Wolves), Kenny McLean (Aberdeen), Matt Phillips (QPR), Robert Snodgrass (Hull)
Steven Fletcher (Marseille), Ross McCormack (Fulham), Tony Watt Blackburn, on loan from Celtic)
Scotland squad to face Denmark on 29 March
Craig Gordon (Celtic), David Marshall (Cardiff)
Ikechi Anya (Watford), Liam Cooper (Leeds), Gordon Greer (Brighton), Grant Hanley (Blackburn), Charlie Mulgrew (Celtic), Kieran Tierney (Celtic), Steven Whittaker (Norwich)
Liam Bridcutt (Leeds), Scott Brown (Celtic), Oliver Burke Nottingham Forest), James Forrest (Celtic), John McGinn (Hibernian), Jamie Murphy (Brighton), Matt Ritchie (Bournemouth)
Steven Fletcher (Marseille), Leigh Griffiths (Celtic), Chris Martin (Derby)