As much as a scrum or a 10-man lineout, the eight-man bench has the feel of a game set-piece.

Given replacements didn’t come into rugby laws until the 1968 Lions tour of South Africa, the concept has come a long way. It fell to Ireland’s Mike Gibson to become the first ever replacement when he came on for the injured Barry John during the first Test match in Pretoria.

Tactical substitutions were introduced in 1996, with three replacements allowed, and here we are now with a greatly changed landscape, with eight bench possibilities as well concussion time-outs and blood bins.

With it the majestic second- half sweep of clean shirts has become a more considered tool, a turbo boost in the last quarter of the match. Even more so for Ireland since Joe Schmidt has become involved.

Accompanying Schmidt’s splicing of replacements into the team are high expectations.

Against Italy, Seán Cronin fed off a Rhys Ruddock poach, while Jack McGrath and Fergus McFadden also came into the match to score tries, and replacement Paddy Jackson kicked two conversions.

In all, 27 points came from players who started and 19 came from substitutes.

Schmidt eyes won’t have missed the contribution of Cronin, who has regularly illuminated the RDS with cameo streaks. Cronin is a hooker with an outside break.

“I’m not too sure but if you want to put something like that in the report I’ll be happy to take it,” he says.

Modest, Cronin has shown he has the pace to equal, and beat, back-line players over 40 metres and more. "Again, I'll take that," he says warming to the talk of sprinting. "I'm sure a few of the lads would probably disagree with that but it's good to have a bit of stick, a bit of craic with them in terms of saying I'm up there with the likes of Ferg (McFadden) and Zebo and these kind of lads. It's a bit of banter, anyway."

Adjustments
Schmidt has not dramatically changed the role of the bench but he has made qualitative adjustments. His view is whoever goes in should make an impact.

In that Saturday’s bench should feel comfortable about their places for France, although, management yesterday said they were torn between continuity and flexibility. With Munster flanker Peter O’Mahony fit again, temptation is strong to bring him back.

“It’s just hammered home that we’re the closers, or the finishers,” says Cronin. “That’s something Joe’s brought in and it’s good to have a rapport like that with the coach, that he’s putting faith in you. He’s hammering it home during the week that we’re the guys that could make the difference if the game is close, or we’re there to finish off the job. That’s reassuring for us and it’s a huge positive that since Joe’s come in he’s brought that to the fold.”

There’s a different mindset too. The anthems, the warm up the presidential parade deliver the immediacy of the game. But from the lull of sitting there is no soft landing or adjustment to the pace of the play. Substitutes are short, sharp medicine for ailing games or like last Saturday, where fresh momentum is a tactical imperative.

"Sometimes it is difficult," Cronin says. "Sometimes you might try too hard and things mightn't click.

'Balancing act'
"So I think it's a balancing act, a mixture of coming on and getting your role right, and building yourself into the game, while making sure that you get all your detail right.

“Finding the mix is kind of the crucial factor there. I’ve been coming off the bench with Jack (McGrath) and Marty (Moore). We play our club rugby together and you kind of build up a good relationship there. You know what each guy is looking for, especially in terms of the scrum.

“So yeah, I think it’s brilliant the fact it appears like that from the outside but I think overall it probably does help that the three of us play together and we’ve been doing well. But again this game is a whole new challenge.”

Although Rory Best is commanding in the position, Cronin rises to the challenge with blinding rationality.

“I love going to France and playing. At home the French are a different animal,” he says almost perversely. “But at the end of the day you’re on the field and it’s 30 lads.”

Sometimes that’s just how it looks.