Peterborough midfielder Sam Szmodics has been denied a senior Republic of Ireland debut against Andorra on Thursday evening by injury.
The 25-year-old aggravated an existing shoulder problem in training and will not make the game, which is live on Sky Sports Premier League.
Manager Stephen Kenny said: "Sam Szmodics hurt his shoulder, just a previous injury that he had. He just came down awkwardly on his shoulder.
"It's nothing serious, but it's an injury he had earlier in the season, so that will rule him out."
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Asked if Szmodics would be able to play in Tuesday night's clash with Hungary, Kenny added: "No, I think he'll be ruled out."
Szmodics was called up to Kenny's ROI squad for the first time ahead of their double-header.
The playmaker started his club career at Colchester United before joining Bristol City and then Peterborough in 2020 after an initial loan spell at London Road. He helped Posh to promotion to the Championship this season with 15 goals in 42 appearances in all competitions.
The Republic of Ireland play Andorra on Thursday and Hungary on June 8, with manager Kenny still looking for his first win in charge.
Swansea's Conor Hourihane and Ryan Manning joined the squad on Monday after their defeat in the Championship play-off final.
Skipper Seamus Coleman had already been ruled out of the game with a hamstring problem.
Uncapped Andrew Omobamidele, Jamie McGrath, Daniel Mandroiu and Chiedozie Ogbene are available and Kenny will not abandon his plans to hand chances to blossoming talent despite the pressing need for a victory.
He said: "We want to win, of course we want to win. It's been well-documented that we haven't. We're waiting to win.
"There are several games that we should have won and we didn't, and we're disappointed with that. We've got to go tomorrow and try to get a victory.
"Yes, we will persist with giving players their opportunity because I believe we will get huge gains from that, so it's a good opportunity for a lot of players tomorrow, and that's the objective."
Hourihane: Settled ROI camp can help results
Conor Hourihane is hoping a rare week without disruption can help the Republic of Ireland end their wait for a first victory under Kenny.
Hourihane and his team-mates, who lost a home World Cup qualifier to Luxembourg in March, can afford to take nothing for granted, with ROI still without a win since last November when they beat New Zealand in a friendly.
The Aston Villa midfielder, who spent the second half of last season on loan at Swansea, said: "It's been tough for the lads over the last year. The amount of transition and chopping and changing in our squad has been huge.
"It hasn't been easy. Covid really hit the squad, injuries, close contacts... It hasn't been easy. The numbers changing in some squads has been ridiculous, 12, 13, or 14 players - and I don't think a nation like Ireland can have that many players out.
"It hasn't been easy, but it is what it is. Hopefully Covid is heading in the right direction and the main squad will be here as much as possible with no disruptions."
Ireland's performances since Kenny replaced Mick McCarthy at the helm have not been without positives - they were very unfortunate to lose their Euro 2020 play-off semi-final in Slovakia on penalties and performed admirably in a 3-2 defeat in Serbia in their opening qualifier of the new campaign.
However, as long as they remain without a win, they know the question will continue to be asked.
Hourihane said: "We all know and want that to be the case, that we get that monkey off our back and get the win we all want and keep moving in the right direction.
"There will always be that little bit in your head that you are desperate to get that result. But I think everyone just needs to breathe and relax a little bit. It will come if we keep doing the right things."