from http://www.rugbyunionrules.com
A rugby union team consists of 15 players: eight forwards, numbered 1 to 8, and seven backs, numbered 9 to 15. Depending upon the competition, there may be up to seven replacements (substitutes or reserves). Professional rugby contains seven reserves, with a player being allowed to be substituted only once.
Rugby union positions
1 Loosehead
2 Hooker
3 Tighthead Prop
4 Lock
5 Lock
6 Blindside Flanker
8 Number 8
7 Openside Flanker
9 Scrum Half
10 Fly-half
11 Left Wing
12 Inside Centre
13 Outside Centre
14 Right Wing
15 Fullback
unless they are a front-row specialist player and are replacing an injured front-row player. Another exception to this rule is the “blood bin”, where a player with a visible and bleeding injury must leave the field and then return to continue play after receiving treatment providing this is within 15 minutes of the player leaving the field (actual time, not game clock). A player sent to the blood bin may be replaced by another player during treatment. If the bloodied player returns to play within 15 minutes, it is not counted as a substitution.
The main role of the forwards is to gain and retain possession of the ball. They take part in set pieces of the scrum and the line-out. Generally, forwards are larger than the backs, which generally makes them stronger but slower. Forwards also have a role in taking the ball forwards, but generally do so by driving into the opposing forwards. Increasingly back row forwards such as flankers and the number 8 are becoming athletic and fast, staying out of the breakdown to participate in running moves with the backs.
The role of the backs is to move the game forward by running or kicking the ball. The scrum-half will gain possession of the ball from the forwards and usually feed it to the fly half also known as the outside half (no.10) who then controls how the attacking team will proceed. The backline will tend to score its tries by focusing on the tactical placement of players, creating holes in the opposition defense line. A successful backline will cause the opposition defense to commit too many players at strategic points creating space to open up for the faster, outside backs (wingers and fullback).
All members of the starting 15 wear jerseys, numbered from 1 to 15, and keyed to their positions. The first eight players, known as forwards or the pack, play in the scrum. The remaining seven players are the backs.
