Scales made his Celtic debut in last month's Scottish League Cup win over Raith Rovers
Celtic defender Liam Scales has replaced the injured Ryan Manning in the Republic of Ireland squad.
Scales, 23, linked up with the squad on Wednesday before they travelled to Baku where they will face Azerbaijan in a World Cup qualifier.
The Under-21 international made his first appearance for his new club in Celtic's 3-0 Scottish League Cup win over Raith Rovers on 23 September.
He joined the Glasgow side from Shamrock Rovers in the summer.
The Republic travel to Azerbaijan without captain Seamus Coleman, knowing their chances of reaching next year's World Cup are already over having taken two points from five qualifying matches.
Scales will be hoping to make his senior debut either on Saturday or three days later when the Republic return home to host Qatar in Dublin.
Republic of Ireland squad
Goalkeepers: Bazunu (Portsmouth, on loan from Manchester City), Kelleher (Liverpool), Travers (Bournemouth)
Defenders: Doherty (Tottenham Hotspur), Christie (Fulham), Duffy (Brighton), Egan (Sheffield United), Stevens (Sheffield United), Scales (Celtic), McClean (Wigan Athletic), Omobamidele (Norwich City), Collins (Burnley)
Midfielders: Cullen (Anderlecht), Hendrick (Newcastle United), Hourihane (Sheffield United, on loan Aston Villa), Arter (Nottingham Forest), McGrath (St Mirren), Knight (Derby County)
Forwards: Robinson (West Brom), Connolly (Brighton), Collins (Cardiff City), Horgan (Wycombe Wanderers), Idah (Norwich City), Parrott (MK Dons, on loan from Tottenham Hotspur), Keane (Wigan Athletic), Ogbene (Rotherham United).