Kieran Marmion, Will Addison and Jordi Murphy remain with the Ireland squad despite missing out on World Cup selection.
The trio lost out on "narrow margins" head coach Joe Schmidt told reporters ahead of Saturday's game with Wales in Dublin.
"[They reacted] unbelievably," Schmidt said of breaking the news to the players, who would all have harboured realistic expectations of making the cut.
"I spoke to them on the phone, I said 'look, this is not the phone call you want to get, you have fallen outside the squad and there's some narrow margins'.
"We discussed a few game-related things with them. Those three guys as young men would be brilliant in the squad, they would contribute without a doubt, but we can only have 31.
"It's very easy for some people on the sidelines to throw barbs on who missed out, you can only find 31 spots, three guys, unbelievably good.
"[We asked them] 'would you come in train Monday, Tuesday, potentially later in week?'
"[They replied] 'be there, no problem'.
"It gives us confidence as well that if we lose someone Saturday, we could definitely lose someone in the tournament, to have them training and up to speed would be profitable for us."
Schmidt indicated that the three players would be kept close but did not say they would be released for their provinces for the first game of the Guinness Pro14 campaign, which starts on 27 September, five days after Ireland face Scotland in Japan.
"That's not this weekend so it’s an opportunity at the moment for them to stay very close to the squad," said Schmidt.
"That wasn’t for today to make that decision. It’s more likely that we’ll make that decision [later].
"I spoke to all the provincial coaches on Sunday evening so they have a pretty good idea about what’s likely to happen with those players.
"I think the important thing is the player themselves if they’ve been left out of the squad after having done a really big block of work if they get freshened up a little bit and then get into the Pro14.
"I think everyone is slightly better off including the individual player who then feels freshened and ready to go."
"It shows the mark of those guys that they are willing to come in; they know that they could be needed," added Johnny Sexton.
Schmidt said that Joey Carbery is the only player who may not be considered for selection. The out-half would need to train fully on Thursday before coming into the coach's thoughts.
Sexton is will make his first appearance of the season after the head coach confirmed the out-half would start.
Robbie Henshaw, Keith Earls and Cian Healy are all available for selection.
Obviously gutted not to be on the plane, thanks to everyone for their kind messages. Best of luck to all the lads involved 👍🏼
— Devin Toner (@DevinToner4) September 3, 2019
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