Stephen O’Donnell has been called up to the Scotland squad while Barry Douglas has withdrawn before the matches against Peru and Mexico.
It is a first senior call-up for Kilmarnock’s O’Donnell, 26, who won one Scotland Under-21 cap in 2013.
The former Partick Thistle and Luton defender helped Killie finish fifth in this season’s Premiership.
Wolves left-back Douglas, 28, made his international debut in Scotland’s March win away to Hungary.
Seven uncapped players were included in national head coach Alex McLeish’s original squad, with the match against Peru kick off at 02:00 BST on 30 May and the meeting with Mexico at 01:00 on 3 June.
Hearts’ John Souttar and Jon McLaughlin, Hibernian’s Lewis Stevenson and Dylan McGeouch, Aberdeen’s Graeme Shinnie, Celtic’s Lewis Morgan and Millwall goalkeeper Jordan Archer as well as O’Donnell, could win their first senior caps.
Revised Scotland squad
Goalkeepers: Jordan Archer (Millwall), Allan McGregor (Hull City) Jon McLaughlin (Hearts)
Defenders: Jack Hendry (Celtic), Scott McKenna (Aberdeen), Charlie Mulgrew (Blackburn Rovers), Stephen O’Donnell (Kilmarnock), Callum Paterson (Cardiff City), John Souttar (Hearts), Lewis Stevenson (Hibernian).
Midfielders: Stuart Armstrong (Celtic), Ryan Fraser (Bournemouth), Dylan McGeouch (Hibernian), John McGinn (Hibernian), Kenny McLean (Aberdeen), Scott McTominay (Manchester United), Jamie Murphy (Brighton & Hove Albion, on loan at Rangers), Matt Ritchie (Newcastle United), Graeme Shinnie (Aberdeen), Ryan Christie (Celtic, on loan at Aberdeen).
Forwards: Oli McBurnie (Swansea City, on loan at Barnsley), Lewis Morgan (Celtic, on loan at St Mirren), Matt Phillips (West Bromwich Albion), Johnny Russell (Sporting Kansas City).