England coach Eddie Jones calls them the "finishers", those players he summons from the bench to close out games that need to be won, rescue those that look like they might be lost, or confirm a victorious platform.
Their efficacy now in England is itself temporarily finished, as they decline; but the concept remains vivid, not just in rugby.
Every sport has its 'super subs', weapons waiting to be deployed for maximum impact.
In US sports, one individual can be called upon to make a decisive influence. The most famed baseball closer of all time was Mariano Rivera of the New York Yankees; 608 saves in 18 years, 300 ahead of his nearest rival.
Closer to home, super subs have entered GAA folklore, from Seamus Darby to Kevin McManamon.
Teams that start games are not the same as those that finish them. And the changes can make the difference - either way.
Adam Griggs yesterday went out to bat on behalf of his bench as they prepare to follow up last week's thumping 45-0 win against Wales by facing the rather more fearsome challenge provided by World No.4 France.
"We always talk about the bench being our 'spark plugs'," the Australian said. "We want them to bring a point of difference and energy. The message to them is that they have had a chance to see how the game is unfolding and you have to go on there and change the picture.
"We've been in a cycle between World Cups where we have to make sure we build a new group, and the bench is part of that."
While it is almost impossible to compare the twin challenges of the woeful Welsh and the formidable French, a neutral observer might survey the impact of last week's bench and worry for the Irish this weekend.
From a half-time position where they were 31-0 up and cruising, dominating every facet of play in a relatively error-free, physically and tactically controlling display, Ireland disintegrated in the second half.
Viewed baldly, the steady disruption of the starting XV was in direct proportion to a worsening performance, as the set-piece crumbled and the phased play fell to pieces, albeit partially amended by piling another 14 points on their feeble victims.
It fed the perception of some that there remains a vast gulf between a very decent starting XV and those bubbling under.
Far from being "spark plugs", it seemed that when Ireland pulled the plug on their starters, it was as if someone switched off the power.
From his vantage point, Griggs' intense analysis espied a subtly different picture which imbues him with much more faith than others in his reserves.
"When we went back over our individual bench impact, they did paint a different picture individually, but, as the game unfolded, the collective understanding fell away and our core skills let us down," he said. "But the individuals did what they were asked. The only way you can get experience is by doing it so it's not something that concerns me.
"I'm happy that as long as they're watching the game, they know what is required of them to change things up and add energy. I'm comfortable with them coming on and adding that."
Griggs is adamant that after that fitful middle period, Ireland eventually got to the finishing line mirroring some of the cohesion with which they had exploded into the contest.
And those who started the game were not utterly exonerated either, despite the fact that Griggs has kept faith with all XV, Ireland unchanged in Test rugby for the first time in six years.
"Talking about the balance of our bench, as a coaching group we looked at it and we looked at the players on the field and we gave them time to rectify some of the things that weren't quite going right," he said.
"And then when that kind of got away on us, we decided to make some changes. So as we got into the last kind of 10, 15 minutes and we had a full bench on, I thought they added to that."
As there are two changes on the bench, again the perception might be that they weren't effective enough last week - the company argument is that competition is developing apace.
Added to hooker Emma Hooban, the presence of another wing speedster to rival the impact of Beibhinn Parsons - Amee-Leigh Murphy Crowe - could be a real game changer from the pine.
Afforded another week of integration into the longer version of the sport, the 25-year-old knows how to get the job done; during a prolific 2018-19 World Series circuit, she made 35 touchdowns.
"There is no secret about Amee-Leigh's athletic ability, how dynamic she is. She brings that x-factor to the Sevens stage," added Griggs. "She is still learning some of the intricacies of the game."
Not yet trusted to start, perhaps. But like the rest of her bench, many are banking on their ability to finish.