Ian Madigan has spent the last year working behind the scenes to prepare to cover scrum-half for Ireland at the Rugby World Cup.
Ireland head coach Joe Schmidt has gambled on taking just two recognised scrum-halves to the World Cup, omitting Isaac Boss and Kieran Marmion.
Fly-half Madigan has quietly beavered away at adding yet another string to his backline bow at Schmidt's behest, and has now started to run in at nine in training this week.
Confirming prop Cian Healy is finally fit after neck surgery in May but may not be risked against England this weekend, Schmidt insisted Ireland will only turn to Madigan at scrum-half in an emergency.
"I'd like to think it's a calculated risk," said Schmidt of selecting two scrum-halves in his final 31-man World Cup squad.
"We've given it as much thought as we could.
"Isaac (Boss) did very well against Scotland.
"That physical aspect of his game is something we'll miss.
"To a degree that risk is managed by the 48-hour rule and the opportunity to get someone in within that time frame before a match if there is an injury.
"With the proximity of the tournament being hosted in England that definitely eased the scenario.
"Ian has done a lot of individual training there, but it's only in the last week he's started to slot in and do a little bit at nine with the team.
"It's been in the back of our minds for a while, but probably not in the forefront.
"I spoke to Ian about it last season, so it's not suddenly something that's sprung up.
"And then he did some work on it in the off-season.
"He's been quietly preparing himself for that potentially to happen.
"But honestly it probably wasn't what we were going to do."
Boss and Marmion remain on injury-cover standby, with Ireland launching their Pool D campaign against Canada in Cardiff on September 19.
Schmidt's men face England in their final warm-up match at Twickenham on Saturday, with Leinster wrecking-ball prop Healy fit again after a frustrating absence.
Munster flyer Keith Earls suffered a heavy blow to the head in last weekend's 16-10 defeat to Wales in Dublin, and is now following the concussion protocols but will not feature against England.
"Cian's cleared to play, he's fit to play," said Schmidt.
"He's been in and out of sessions but not doing the whole session.
"He's acquitted himself well on his first two days, so we thought we'd have a look at how that goes on Thursday.
"And Keith's very good: he is following the return to play protocols.
"He hasn't trained with the team, he won't be involved at the weekend but I'd say he'd be cleared to play by the weekend following the protocols because there are no recurring problems."
Ulster wing Andrew Trimble was the biggest fall-guy with provincial mate Darren Cave sneaking at centre thanks to Madigan covering scrum-half.
Leinster's 22-year-old bolter Tadhg Furlong will cover both loosehead and tighthead prop, with Schmidt keen to retain "specialist" centre Cave.
"That was the most discussed position," said Schmidt of Trimble missing out.
"He'd played 34 minutes of a Test match and 80 minutes for Ulster but in between that he hurt his foot again, it interrupted his preparation and time ran out for him."