BRITISH & Irish Lions full-back Rob Kearney has had to sidestep the November international series to put right a back injury that will take him out of rugby for two months.
THIS leaves a void at No 15 that will be filled by either the repositioning of Keith Earls or Tommy Bowe from the wing or by the promotion of Leinster's Ian Madigan, Munster's Ian Keatley or Denis Hurley or Connacht's Robbie Henshaw.
In effect, there is a personal play-off between these four players for the right to join the Ireland squad at a time when coach Declan Kidney has already shown faith in the youth of Ulster's Iain Henderson (20) and Luke Marshall (21), Munster's Dave Kilcoyne (23), as well as Leinster's Ireland-qualified Richardt Strauss.
The most interesting point is that three of the four players have been pushed out of position to fill in for others and now find themselves on the brink of an international breakthrough. Hurley is the only 'bona-fide' full-back.
Madigan and Keatley are more renowned as out-halfs, while Henshaw, not long out of Marist College in Athlone, has been here-to-fore seen as an outside centre, where he played for the Ireland Schools just 18 months ago.
Madigan has started the first two rounds of the Heineken Cup at fifteen for Leinster, making significant progress from a sketchy performance against the Exeter Chiefs to a secure impact against The Scarlets last Saturday.
The management are known to be keen on the prospect of introducing 19-year-old Henshaw, who plays with an old head on very young shoulders.
It could just come down to which individual looks the most composed this weekend and the provincial selections should give a strong indication as to who could make it at full-back, especially with Hurley and Keatley vying for involvement at Munster.
There is also a place left open at tight-head prop where Ulster's Declan Fitzpatrick, Munster's Stephen Archer and Sale Shark Tony Buckley will all audition for the role in League action this weekend.
This area is still the one that causes most worry as Kidney hinted that he would not be in favour of asking Ulster's Tom Court to cross over from loose-head to tight-head.
In total, there are 10 Leinster players included in the squad of 31, 10 from Ulster, nine from Munster and two from Connacht with the possibility of two more players being added to the squad after this weekend's PRO12 League matches.
Coach Kidney has also made changes to his management team, Anthony Foley taking over as defence coach to allow Les Kiss more scope to develop Ireland's attack. Greg Feek will once again act as the scrum coach.
IrELAND squad: Rory Best (Ulster), Tommy Bowe (Ulster), Darren Cave (Ulster), Tom Court (Ulster), Gordon D'Arcy (Leinster), Keith Earls (Munster), Stephen Ferris (Ulster), Cian Healy (Leinster), Jamie Heaslip (Leinster), Iain Henderson (Ulster), Chris Henry (Ulster/), David Kilcoyne (Munster), Luke Marshall (Ulster), John Muldoon (Connacht), Conor Murray (Munster), Mike McCarthy (Connacht), Fergus McFadden (Leinster), Kevin McLaughlin (Leinster), Donncha O'Callaghan (Munster), Paul O'Connell (Munster), Brian O'Driscoll(C) (Leinster), Ronan O'Gara (Munster), Peter O'Mahony (Munster), Eoin Reddan (Leinster), Mike Ross (Leinster), Donnacha Ryan (Munster), Jonathan Sexton (Leinster), Richardt Strauss (Leinster), Andrew Trimble (Ulster), Dan Tuohy (Ulster), Simon Zebo (Munster).