England's head coach Eddie Jones lists them as 'finishers' on his team sheet, other coaches choose more traditional terminology. But there is universal agreement, whatever the label applied, that rugby is a 23-player game and that the phrase 'impact off the bench' is highly desirable if it peppers the post-match analysis.
This column came across statistics compiled by Russ Petty, a freelance rugby writer and contributor to Rugby World magazine, in which he looked at the use of replacements by Tier One nations in rugby in the period from 2016-2018.
The most striking figure was that gleaned from New Zealand matches during that period.
The All Blacks played 38 Tests and on every single occasion all eight replacements were used. There were just five French players who didn't get a game in 29 Tests and 11 apiece in the case of Argentina and Italy. During the timeframe in question 16 Ireland players were unused replacements in 31 Test matches.
Given the current speculation with regard to whether Conor Murray will line out against the All Blacks on Saturday, November 17th, not having played a game since the summer Test series win over the Wallabies in Australia, it's germane to examine how the numbers break down from an Irish perspective.
On 20 occasions in 31 matches, Ireland head coach Joe Schmidt has used all eight replacements while at the other end of the scale there are five games in which two players didn't get a minute and four of those relate to the replacement halfbacks.
The first time it occurred was when replacement halfbacks Kieran Marmion and Ian Madigan stayed in the stand as Ireland beat South Africa 26-20 in the first Test on the summer tour in 2016. Paddy Jackson (16 points) and Conor Murray (a try) played the 80 minutes.
The only Test when there were two unused replacements and they weren't specifically the replacement halfbacks was the famous victory over the All Blacks in Chicago (2016), when Marmion and Garry Ringrose didn't see any game time.
In the opening match of the 2017 Six Nations, Ireland lost 27-22 to Scotland at Murrayfield with Jackson and Murray playing the full match; Marmion and Ian Keatley remained on the bench for the duration.
The next occasion was the opening game in last season's Grand Slam-winning Six Nations campaign, Johnny Sexton's drop goal, to go with his four penalties, edging the team to a dramatic 15-13 win against France in Paris. Luke McGrath and Joey Carbery watched from the bench.
The most recent occasion was during the third Test last summer when Ireland beat the Wallabies 20-16; Marmion and Ross Byrne watched Murray and Sexton (five penalties) steer Ireland home.
To offer some context in those five Tests, four victories and a defeat, there was only the game in Chicago in which Ireland won by more than seven points, but in that match, Schmidt’s side led by just four points, 33-29, until Robbie Henshaw’s 76th minute try, with Carbery then tagging on the conversion to leave them 40-29 victors.
Connacht scrumhalf Marmion is definitely the 'unluckiest player' having been an unused replacement on six occasions, although his misfortune is still some way short of the late Paddy Madigan.
The former Old Belvedere hooker made 15 appearances for Leinster, played in several Final Trials, and sat on the bench on more than a dozen occasions for Ireland without getting capped. In those days only an injured player could be replaced.
His grandnephew, Ian, who scored 131 points in 30 appearances for the national side, twice missed out on adding to both tallies, as he was an unused replacement against Scotland and South Africa in 2016, while eight different players have been unused replacements during an Ireland Test.
The breakdown in terms of position is five outhalves (Madigan, Jackson, Keatley, Carbery and Ross Byrne), three scrumhalves (Marmion, Eoin Reddan and McGrath), a prop (Finlay Bealham) and a centre (Ringrose).
For those who may believe that Ireland are an exception in not replacing their scrumhalf, South Africa’s Faf de Klerk played all bar eight minutes in five matches in the recent Rugby Championship.
Murray and Sexton are hugely important to the Ireland team but this four-match Test window offers some scope to examine what lies below in the pecking order, particularly but not exclusively in the Italy and USA matches. Also it seems counterintuitive in Murray’s case to rush him back, both in terms of the risk involved and the message it would send to the other three scrumhalves.