The Ireland rugby coach Joe Schmidt named just two recognised halfbacks in his World Cup squad and will rely on first-five Ian Madigan as emergency cover to allow Darren Cave travel as specialist backup at centre.
The Six Nations champions have no fresh injury concerns ahead of their first game against Canada on September 19th and included prop Cian Healy, currently recovering from injury, in a full strength 31-man panel loaded with depth.
Winger Andrew Trimble, Ireland's breakout performer in their first of two successive Six Nations triumphs in 2014, missed out in the most competitive spot after playing just 34 minutes of rugby in the last eight months.
While some coaches have opted to bring two hookers, Schmidt followed Australia's Michael Cheika in gambling at halfback.
However, unlike Matt Giteau who has played there for the Wallabies, Madigan has little experience at number nine.
Schmidt said last week that Madigan had not trained at halfback with Ireland, but did recall the slick passer training there during the New Zealand coach's time in charge of Leinster.
"There were some very tight decisions, particularly in the back three and it was also a challenge to make sure that key positions were covered as much as a squad of 31 players allows," Schmidt said in a statement.
"A number of players were very unlucky to miss selection."
Competition was so intense in the back three that only fullback Rob Kearney was a sure selection with Tommy Bowe, Ireland's third highest try scorer of all time, not certain of a place until Schmidt named the squad of 17 forwards and 14 backs.
The in-form Dave Kearney and Simon Zebo were the other out-an-out wingers included -- with Munster's Zebo also providing cover at fullback -- while the versatile Keith Earls and Luke Fitzgerald will also be pushing for a start.
In the pack, backup tighthead props the New Zealander Nathan White and Tadhg Furlong, who have just three caps between them, beat Marty Moore in another tight call after injury kept Moore out of the recent warm-up games.
Paul O'Connell will captain the squad that will also face Romania, Italy and France as Ireland seek to progress beyond the quarter finals of a World Cup for the first time.
Forwards: Rory Best, Sean Cronin, Tadhg Furlong, Cian Healy, Jamie Heaslip, Iain Henderson, Chris Henry, Jack McGrath, Jordi Murphy, Sean O'Brien, Paul O'Connell (captain), Peter O'Mahony, Mike Ross, Donnacha Ryan, Richardt Strauss, Devin Toner, Nathan White.
Backs: Tommy Bowe, Darren Cave, Keith Earls, Luke Fitzgerald, Robbie Henshaw, Paddy Jackson, Dave Kearney, Rob Kearney, Ian Madigan, Conor Murray, Jared Payne, Eoin Reddan, Jonathan Sexton, Simon Zebo.