Full-backs Alan Hutton and Lee Wallace and striker Chris Martin have withdrawn from the Scotland squad for their friendlies against Italy and France.
Scotland play Italy in Malta on Sunday, 29 May and Euro 2016 hosts France in Metz on Saturday, 4 June.
The Scottish FA has given no further details on the trio pulling out and no replacements have been named yet.
Last week, Scott Fox, Jack Hamilton, Stephen Kingsley and Craig Bryson were drafted in to cover for absent players.
Barry Bannan, Robert Snodgrass, Shaun Maloney, Andrew Robertson and Allan McGregor are all involved in the English Championship play-off final the day before the game against Italy, while Dundee goalkeeper Scott Bain has a back problem.
Rangers captain Wallace was returning to the squad after a long absence, having last been capped in November 2013.
Aston Villa's Hutton made his 50th international appearance in the 1-0 win over Czech Republic in March, while Derby forward Martin has scored once in eight matches for Gordon Strachan's side.
Revised Scotland squad:
David Marshall (Cardiff), Scott Fox (Ross County), Jack Hamilton (Hearts)
Christophe Berra (Ipswich), Gordon Greer (Brighton), Grant Hanley (Blackburn), Russell Martin (Norwich), Charlie Mulgrew (Celtic), Callum Paterson (Hearts), Andrew Robertson (Hull), Stephen Kingsley (Swansea)
Ikechi Anya (Watford), Barry Bannan (Sheffield Wednesday), Oliver Burke (Nottingham Forest), Darren Fletcher (West Brom), Shaun Maloney (Hull), James McArthur (Crystal Palace), John McGinn (Hibernian), Barrie McKay (Rangers), Matt Phillips (QPR), Matt Ritchie (Bournemouth), Robert Snodgrass (Hull), Craig Bryson (Derby County)
Steven Fletcher (Marseille), Ross McCormack (Fulham), Steven Naismith (Norwich)