Mark Tainton unclips a fun grenade. “Yeah, there are a number of players who could be in with a shout for a start against Argentina,” says the Ireland assistant coach, throwing a glance across the table at Peter O’Mahony.

The Munster backrow replies with a sheepish smile and when Tainton raises the name of Ulster’s Iain Henderson as one of those who caught the eye against Fiji and might well also be in “with a shout” it seems the only way out is for O’Mahony to throw himself on the device and stifle a laugh.

O’Mahony has been one of Ireland’s transition players, a descriptive term he doesn’t quite understand; the way he sees it is there’s a myriad of new faces in the Ireland camp who have emerged out from the shadows of players like Seán O’Brien, Kevin McLoughlin, Shane Jennings, Denis Leamy and David Wallace; some of whom will return, others not. But transition is an appropriate term for O’Mahony, an impressive figure this season, caught in the eye of the storm of changing times.

A natural leader, he has captained Ireland at Under-18 and Under-20 levels and made his senior debut against Italy in February of this year, coming on as a replacement for the lionised O’Brien.

First start against Scotland

He made his first start for Ireland in the game against Scotland in March after an injury to O’Brien and replaced the equally celebrated Stephen Ferris as Ireland’s blindside flanker in the first Test against New Zealand in June.

He came off the bench during the second Test a week later and replaced current Ireland captain Jamie Heaslip at number eight. Eight caps on and he has played for Ireland in all three backrow positions.

“I don’t know what that word transition is,” he says. “Every team goes through a stage were there are young guys knocking at the door.

“We’re lucky enough to have a big group coming through at once. I think it’s given everyone a lift, even the older fellas in the group, they’re getting a kick and a buzz out of the younger fellas being around and adding their two cents’ to training. I think everyone is learning from it.”

Transition: upheaval, metamorphosis, development, flux.

“It brings a different perspective on things. The game of rugby is always evolving and to bring younger players through who have a different perspective on things is great for everyone.

“I’m sure Declan Kidney is learning off some of the young fellas as much as Donners (Donncha O’Callaghan) is and Rog (Ronan O’Gara) and Jamie (Heaslip) and the guys who have loads of caps. They are learning off fellas as much. We are learning a lot more than they are learning off us but it’s great, I think.”

Carried away

O’Mahony was in the stadium watching Ireland exploit Fijian lethargy and as he puts it, probably getting “a bit carried away in the stands watching the game, shouting on the lads”.

In his rugby world there are a lot of new things. Cheering on those who would tear the shirt from his back smacks of wilful innocence and perhaps too that is a strength.

Blessed in the Munster tradition of being free of any bull, the anticipated hand to hand against Argentina is a welcome, possibly defining challenge, given the importance of the match for World Cup ranking.

“It’s going to be physical, yeah,” he says. “As a 15 we’re going to have to front up, everyone. Breakdown is where international games are won these days and that’s where we are going to be focusing. Not just one day, not just the pack, it’s a backs issue now as much as a forwards. We’re going to look for a physical performance from one to 15.

“They are a very potent side, very dangerous. Obviously the backrow Leguizamon (Juan Manuel) and Lobbe (Fernandez) . . . these guys are playing top class rugby and since they’ve got into the Rugby Championship they have really improved. They haven’t got away from what they were good at and have added other things. That’s made them more of a rounded team. But we’ll be looking at ourselves.”

Of the 32 players present in the squad there are 17 faces that were not at the World Cup just over a year ago.

The game against Fiji and the more liberated impulses of the younger players may have accelerated the pace of change, maybe opened the eyes of older soldiers. But it’s ideas that are generally the most heretical.

“We are talking about creating our own legacy,” says O’Mahony.