"Unfortunately Keith's baby daughter has been taken ill and is in hospital as we speak. The nature of the illness is unclear, however I did speak to Keith this morning and he was hopeful and optimistic that the baby would get home some time over the weekend.
"The decision was taken following a conversation between Declan (Kidney) and Keith yesterday and it was thought that it was in the best interests of Keith and his partner and their families that Keith remains in Limerick for the weekend.
"Fergus comes in, instead of Keith, and David Kearney has taken Fergus' place on the replacements bench."
Sunday's match will represent McFadden's third start in the RBS 6 Nations, following two runs on the right wing against Italy and France last season.
The 22-year-old Kearney joins his older brother Rob and fellow uncapped player Peter O'Mahony in the matchday 22.
IRELAND Team & Replacements (v Wales, 2012 RBS 6 Nations Championship, Aviva Stadium, Sunday, February 5, kick-off 3pm):
15 - Rob Kearney (UCD/Leinster)
14 - Tommy Bowe (Ospreys)
13 - Fergus McFadden (Old Belvedere/Leinster)
12 - Gordon D'Arcy (Lansdowne/Leinster)
11 - Andrew Trimble (Ballymena/Ulster)
10 - Jonathan Sexton (St. Mary's College/Leinster)
9 - Conor Murray (Garryowen/Munster)
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 - David Kearney (Lansdowne/Leinster) *
* Denotes uncapped player