Earls will start at outside centre against Wales on Sunday, filling the void left by the absence of Brian O'Driscoll who is to miss the entire championship after undergoing shoulder surgery.
The 24-year-old's selection in a position O'Driscoll has occupied with such distinction since 1999 comes just days after his partner Edel McGee gave birth to their baby girl, Ella-Maye.
He returns to the Irish camp tonight after playing only a limited role in training for the past week.
Coach Declan Kidney, however, is keen to keep a sense of perspective over the occasion.
"There's a lot of things happening for Keith at the moment and he's buzzing," he said.
"It's extenuating circumstances and whereas he wasn't the one to have the child, it's still a big day for any man, so we've tried to give him a bit of space.
"We must remember these guys are people first and players second.
"When something like this happens in your life it's only right that you're given some space.
"If it's your first you're inclined to take a day or two to enjoy it.
"Maybe if it's your fifth or sixth you wouldn't be taking the day off!
"Life is like that sometimes - you just have to go with the flow."
Fergus McFadden, Tommy Bowe and Andrew Trimble were also in the frame to partner Gordon D'Arcy in midfield, but Earls has had greater exposure to the position.
In recent weeks Ireland's leading try-scorer at last autumn's World Cup has played at 13 for Munster, excelling against Northampton but otherwise having only limited impact.
"Keith is looking forward to it and has played well there for Munster," said Kidney.
"Players just want to play so they know they need to adapt. Keith's had a lot of time at 13 and is comfortable there."
The in-form Trimble has been selected on the left wing with Jonathan Sexton and Conor Murray the preferred half-backs.
Sexton has edged out the more experienced Ronan O'Gara, who must settle for a spot among the replacements.
In total there are only three changes, one positional, to the side defeated 22-10 by Wales in their World Cup quarter-final.
The pack is identical to the eight that suffered heartache in Wellington with Donncha O'Callaghan holding off the challenge of Donnacha Ryan in the second row.
The only Test debutant in the 22 is Munster back row Peter O'Mahony, who features on the bench.
Kidney is sure to be criticised for what will be perceived by some as a conservative selection, but retains faith in his established internationals.
"I respect everybody's view. This team is everybody's team, people talk about who should and who shouldn't be playing," he said.
"Players need to work their way into the team. All the guys picked have worked hard to get into the team.
"We had a disappointing match on our last day out, but one bad game doesn't make you a bad team.
"Wales played very well that day and if we play the same way on the Sunday then it will be the same result.
"Wales are a very good side - you don't get to the World Cup semi-finals if you're not.
"Listening to all the noises they making, they're purring at the moment."
Wales, who are waiting for injury updates on key players Rhys Priestland, Dan Lydiate and Jamie Roberts, name their team for the showdown in Dublin on Friday.
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