Joe Schmidt wants Garry Ringrose to "continue to grow" and said the Leinster man's centre partnership with Robbie Henshaw has simply been too promising to disrupt.
Schmidt has decided to stick with the 15 who started against France for the huge Friday night showdown in Wales.
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That means that the fit-again Jared Payne missed out completely, failing to make the match-day 23, and 22-year-old Dubliner Ringrose gets another chance to shine on the big stage.
And at the Principality Stadium, in front of a home crowd desperate for a backlash from their team, the stakes could hardly be higher.
"Sometimes you're almost happy you don't have to make calls, but Robbie and Garry had a really good relationship and were building on that so sometimes a selection might be swayed because of that cohesion of the current combination," said Schmidt.
"At the same time Jared and Robbie had played a lot together as well. I think Jared's experience potentially even off the bench would have been handy because he's played on the wing in his long-distant past and he can play in the midfield. So his versatility is another asset.
Robbie and Garry had a really good relationship and were building on that
"He's contributed hugely in the past but you've got to keep your rhythm in this competition, you've got to keep improving. We've got combinations we do feel are improving and we want to give them an opportunity."
Schmidt also highlighted a key moment for Ringrose at the Aviva Stadium two weeks ago as a real barometer of his progress: "I think Garry played really well against the French. Some of his defensive work was outstanding.
"His tackle on [Guilhem] Guirado on the 22 when he closed the space so quickly and got such good contact... those are the things we see as growth points for Garry compared to the start of the championship when he didn't have that confidence.
"We want him to continue to grow in that manner."
Wayne Barnes [below] will be the man in the middle at Cardiff, an appointment that filled some Ireland fans with a sense of trepidation.
Ireland have lost more games under Barnes's watch [nine out of 13] than any other ref, but Schmidt praised the Englishman, and is confident he'll exert control in what promises to be a white-hot atmosphere.
"There are so many laws, so many different pictures to see that it's nice to have one of the better referees," Schmidt said.
"Last time [against France] there were frustrations because I think there was a zero tolerance around falling on the wrong side of the tackle in the first 20 minutes and that ebbed away.
"I understand why because it would have been 13-a-side at the end of the game the way it was going so that tolerance was extended a little bit. Unfortunately in the first 20 minutes we didn't have a lot of ball and we copped the penalties against us.
"We expect the unexpected on Friday evening. What we will expect is a real physical challenge a real front-foot ability to play and that is probably what they;re famous for, that they do play on the front foot."
Live Six Nations coverage of Wales v Ireland on RTÉ Two and RTÉ Player from 7pm on Friday (KO 8.05pm), live radio commentary on RTÉ Radio 1 from 7.45pm and live blog on RTÉ.ie and the RTÉ News Now app.
Live coverage of Wales v Ireland (KO 11.30am) in the Women’s Six Nations on RTÉ Two and RTÉ Player from 11.15am on Saturday.
Live Six Nations coverage of Italy v France (KO 1.30pm) and England v Scotland (KO 4pm) on RTÉ Two and RTÉ Player from 1.20pm on Sunday.
Live coverage of Wales v Ireland in the Under-20 Six Nations on RTÉ Two from 6.15pm (KO 6.30pm) on Saturday.
