So often the focus is on which players are going to be included in the starting line-up, but in many cases game decisive interventions have been made by replacements, or finishers as Eddie Jones calls them.
Especially when games are so physically demanding, the introduction of a substitute can prove pivotal in determining the course of the game, with their sharpness proving too difficult for weary defenders to deal with.
Click through the gallery below to see the 10 most-used replacements:
10. Tomas Cubelli (Argentina) - 31 starts, 44 replacement appearances
9. Eoin Reddan (Ireland) - 26 starts, 45 appearances
5=. Wyatt Crockett (New Zealand) - 25 starts, 46 replacement appearances
5=. Valentin Calafeteanu (Romania) - 54 starts, 46 replacement apperances
5=. Piri Weepu (New Zealand) - 25 starts, 46 replacement appearances
5=. Danny Care (England) - 38 starts, 46 replacement appearances
4. Julian Montoya (Argentina) - Nine starts, 50 replacement appearances
3. Tatafu Polota-Nau (Australia) - 39 starts, 51 replacement appearances
2. Keven Mealamu (New Zealand) - 77 starts, 55 replacement appearances
1. Sean Cronin (Ireland) - 10 starts, 62 replacement appearances