The news comes in the wake of Shay Given's retirement from international football.
Just 48 hours ago Trapattoni expressed confidence his most senior players in Keane, Dunne, Given, as well as Damien Duff, would all return to the fold for the start of the World Cup qualifiers next month.
The quartet, in the wake of their Euro 2012 exertions at the end of what was a disappointing campaign, were given leave by the 73-year-old Italian for this week ahead of Wednesday's friendly with Serbia at the Red Star Stadium in Belgrade.
In Dunne's case, in particular, that has since been superseded by a recent groin operation that will keep him out until the middle of next month at the earliest.
Trapattoni's words, however, were yesterday reinforced by assistant Marco Tardelli as the management at least sang from the same hymn sheet, but then came Given's bombshell late on Monday.
Although confirming he is available in an emergency, it is fair to say he is unlikely to add to his record 125 caps spread over more than 16 years.
Given's decision has now prompted unease in Trapattoni's mind as to captain Keane and defender Dunne especially.
Trapattoni said: "Richard sent me a message recently saying he would not be ready for the game with Kazakhstan because he needs a few weeks to recover from his injury, that the game was too soon.
"I answered him and said after this friendly, after he has recovered from his injury, we would review the situation, but I've told him we need him, it's true. He will let us know.
"As for Robbie, I've also sent him a text, but he's not answered me. I've checked my mobile.
"I will speak with him before I announce my next squad (in around 10 days' time for the Kazakhstan game).
"He needs to tell me whether he wants to come back or what he wants to do.
"We can decide after this game because it's important for us to look at the other players. We have (Shane) Long, (Simon) Cox and (Jon) Walters.
"After this game, and before the one with Kazakhstan, we can think about this situation."
It means the game with Serbia is now more than just a pre-season friendly as it could form the foundation for future squads.
In naming his side, Kieren Westwood now has to fill Given's shoes in being named number one, with Paul McShane, Darren O'Dea, John O'Shea - also wearing the captain's armband - and Stephen Kelly lining up in defence.
Across the middle is Aiden McGeady, James McCarthy, Glenn Whelan and James McClean, with Walters and Long in attack.
"This friendly match is a good opportunity to see some of the new players, to give them a chance to prove they can be part of the national team," added Trapattoni.
"I'm not expecting a great result or a beautiful match because we all know the players are at the start of their season with their clubs.
"But if we can get a good result, that brings confidence and builds the trust within the team.
"When you have young, new players their morale goes down after a defeat, so a good result would give us that confidence and trust."
With the uncertainty surrounding the big-name players, a result would certainly provide a lift for Trapattoni and his squad going into the September 7 clash with Kazakhstan in Astana.
In a qualifying group that also includes Germany, Sweden and Austria, the Republic's chances of reaching the finals in Brazil in 2014 appear slim.
But a defiant Trapattoni said: "It's a tough group, but then the last group (for Euro 2012 qualification) was tough.
"We have to show what we achieved in qualifying for the Euro - we must keep the same attitude, identity and play."
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