Luton striker James Collins will link up with the Ireland squad for their two matches this week.
The forward, who scored his third goal of the season in the 2-1 win over Huddersfield yesterday, had been on standby for the Euro 2020 qualifier with Switzerland on Thursday and friendly against Bulgaria the following Tuesday, both held at the Aviva Stadium.
However, he along with Fulham defender Cyrus Christie and Burton Albion goalkeeper Kieran O'Hara have now been selected, replacing the injured Sean Maguire (eye), Matt Doherty (knee) and Keiren Westwood (knee).
Crystal Palace midfielder James McCarthy is also out of the two games, as manager Mick McCarthy said: "It is hard on the four players to miss out for a game as big as the Switzerland match.
"We have a 24-strong squad now with James, Cyrus and Kieran coming in and we will get to work on Monday.”
Speaking before Collins had been called up once more, Luton boss Graeme Jones said: "I don’t know the Republic of Ireland forwards, that’s the truth, so I don’t know who we’re comparing him to.
"I can only speak about this form since I’ve been involved with Luton and it’s been exceptional, he’s been a pleasure to work with day to day and he takes things on board.
"There is nobody that gives more to the Luton Town cause than him, but he’s got an end product about him, and we've started to see that now, in the Championship as well."
The Ireland squad assembled at the team base in Dublin this afternoon and will begin training at the FAI National Training Centre on Monday.
Republic of Ireland squad
Goalkeepers: Darren Randolph (Middlesbrough), Mark Travers (Bournemouth), Kieran O'Hara (Burton Albion - on loan from Manchester United)
Defenders: Seamus Coleman (Everton), Cyrus Christie (Fulham), Shane Duffy (Brighton & Hove Albion), Richard Keogh (Derby County), John Egan (Sheffield United), Kevin Long (Burnley), Enda Stevens (Sheffield United).
Midfielders: Alan Judge (Ipswich Town), Callum O’Dowda (Bristol City), Alan Browne (Preston North End), Jack Byrne (Shamrock Rovers), Jeff Hendrick (Burnley), Conor Hourihane (Aston Villa), Glenn Whelan (Hearts), Josh Cullen (Charlton Athletic - on loan from West Ham United), James McClean (Stoke City), Ronan Curtis (Portsmouth).
Forwards: Callum Robinson (Sheffield United), James Collins (Luton Town), Scott Hogan (Stoke City - on loan from Aston Villa), David McGoldrick (Sheffield United).