Commenting on the personnel switch and Saturday's clash with France, Ireland head coach Declan Kidney said: "Keith has been bubbling away since he's been back with us and has trained well.
"It was tough on Fergus to lose out because he did a good job for us against Wales last weekend, but Keith is worthy of a start.
"No matter who you're playing, if you're loose with your kicking game, then it's going to give the opposition a chance to counter attack a lot and retain the ball a lot. We know we need to get smarter in that area.
"It's a different team that we're playing on Saturday. You have to watch how much emphasis you put on what happened before, because France present a whole different set of challenges.
"It is important to look back, but certainly with a six-day turnaround, not to look back for too long and just to work forward then towards what's going to be a huge challenge against a team that was in the World Cup final not too long ago."
Lock Paul O'Connell is hoping to captain Ireland to not only their first win of the 2012 Championship, but also a maiden away victory over France since Brian O'Driscoll's hat-trick heroics in 2000.
"There's a lot we have to improve on. Certainly some of the basic errors we made early on," admitted O'Connell.
"We missed touch, the ball we gave to Bradley Davies at the front of the lineout early on, myself going ahead of the kicker - a few little silly mistakes that you just can't make at that level, really those things need to be cut out.
"I think if we can do that early on, it can make a big difference to us. We got off to a bad start and conceded a lot of momentum and a lot of pressure to the Welsh.
"I think against France, particularly away from home, you have to start well. That's going to be important for us."
IRELAND Team & Replacements (v France, 2012 RBS 6 Nations Championship, Stade de France, Saturday, February 11, kick-off 9pm/8pm Irish time):
15 - Rob Kearney (UCD/Leinster)
14 - Tommy Bowe (Ospreys)
13 - Keith Earls (Young Munster/Munster)
12 - Gordon D'Arcy (Lansdowne/Leinster)
11 - Andrew Trimble (Ballymena/Ulster)
10 - Jonathan Sexton (St. Mary's College/Leinster)
9 - Conor Murray (Garryowen/Munster)
1 - Cian Healy (Clontarf/Leinster)
2 - Rory Best (Banbridge/Ulster)
3 - Mike Ross (Clontarf/Leinster)
4 - Donncha O'Callaghan (Cork Constitution/Munster)
5 - Paul O'Connell (Young Munster/Munster) (capt)
6 - Stephen Ferris (Dungannon/Ulster)
7 - Sean O'Brien (Clontarf/Leinster)
8 - Jamie Heaslip (Naas/Leinster)
16 - Sean Cronin (St. Mary's College/Leinster)
17 - Tom Court (Malone/Ulster)
18 - Donnacha Ryan (Shannon/Munster)
19 - Peter O'Mahony (Cork Constitution/Munster) *
20 - Eoin Reddan (Lansdowne/Leinster)
21 - Ronan O'Gara (Cork Constitution/Munster)
22 - Fergus McFadden (Old Belvedere/Leinster)
* Denotes uncapped player