Joe Schmidt admitted it was a calculated risk. Isaac Boss and Kieron Marmion stay at home with Ian Madigan prepared to slot in at scrumhalf if the world falls in on the heads of the Irish nines, Conor Murray and Eoin Reddan.

In that sense Schmidt’s acknowledgment of the danger makes him entirely innocent of belittling the nine position. There is a parachute and he has already explained it. The 48 hour rule to bring in players for injury allows him some latitude.

The coach believes in Madigan, Simon Zebo believes in Madigan and so too does Leinster scrumhalf Luke McGrath. Madigan's wide ranging footballing ability has no lack of admirers.

With former Leinster and current Australian coach Michael Cheika going with Will Genia and Nick Phillips and Matt Giteau fulfilling Madigan's role as a scrumhalf backup, it may be a case of great minds thinking alike.

But former hooker and current Japanese coach Eddie Jones has also opted to go with versatility and includes just two specialists as well.

A difference is Giteau started out on his rugby career at scrumhalf, while Madigan’s outings there have been seen in the same way as sightings of Big Foot and Sasquatch in Yosemite Park.

But McGrath, who could team up with former St Michael’s graduates Ross Byrne and Cathal Mash in Leinster for this week’s second Pro12 game of the season against Cardiff, is a scrumhalf, whereas Zebo is not.

McGrath is not about to sell the requirements and responsibilities in the halfback position too cheaply. But if the cosh comes down, he feels the 26-year-old Madigan’s versatility will see him safely through.

“Well what everyone sees (at scrumhalf) is passing and kicking and stuff like that,” says McGrath of the outsider’s view of playing the position.

“But it’s also scanning, reading the game knowing which options to pick and what players too hit when you are going around the corner - things like that.

“But Mad’s (Madigan) is a brilliant footballer. I’ve no doubt that if he does step in he can do a good job.”

The confidence in Madigan is heart warming and loyal but in some ways blind. Although Schmidt mentioned to Madigan quite some while ago to find some familiarity with position, it takes time to bed in, especially at World Cup level.

“Yeah it does take a bit of time to get used to it,” concedes McGrath. “But I’ve no doubt Mad’s has been slipping in and out with stuff at training. If he does that he’ll have practised it before he goes anyway.”

Indeed but how many times has Madigan "come around the corner" at international level or partnered Johnny Sexton from the other side or bullied the forwards in a rolling maul a la Peter Stringer. It's simple, but not easy.

“No it’s not,” he says cautiously. “The guy down the back (of the room, former Irish scrumhalf and current Leinster manager Guy Easterby) is giving me the eyes...

“It is a difficult position to play but Mads has controlled the game for years at 10 and I think he would be a good suit at nine if he is going to be there, obviously after the two guys.”

Schmidt’s decision is also taken in the light of having more players available to him than in the previous World Cups as he has 31 for Cardiff and London, whereas Declan Kidney had one man less with 30 players travelling to New Zealand in 2011. Boss, Reddan and Murray took the trip as the nominated specialist scrumhalves.

In the hapless 2007 World Cup from Ireland’s Bordeaux base in France, it was Boss, Reddan and Stringer who travelled and before that in 2003 Stringer, Easterby and Ulster coach Neil Doak were selected.

The varying fortunes of each squad was highlighted by Jerry Flannery’s departure in 2011 when late call up Damien Varley replaced the Irish hooker when he tore a calf muscle in training. Doak, although he travelled to Australia in 2003, was not required for any action.

Schmidt and Cheika, however, are not breaking the mould for squad selection. Back in the 1999 World Cup when Wales coach, Warrren Gatland was in charge, he selected just two scrumhalves in Tom Tierney and Brian O’Meara.

Ireland lost to Argentina that year in the quarter-final playoffs.