<P> Substitutes (generally referred to as "the bench") are allowed in the sport, and are typically used when a player gets tired or injured, although they can also be used tactically . Each team is currently allowed four substitutes, and in Australia and New Zealand, these players occupy shirt numbers 14 to 22 . There are no limitations on which players must occupy these interchangeable slots . Generally, twelve interchanges are allowed in any game from each team, although in the National Rugby League, this was reduced to ten prior to the 2008 season and further reduced to eight prior to the 2016 season . If a team has to interchange a player due to the blood bin rule or due to injury, and this was the result of misconduct from the opposing team, the compromised team does not have to use one of its allocated interchanges to take the player in question off the field . </P> <P> The backs are generally smaller, faster and more agile than the forwards . They are often the most creative and evasive players on the field, relying on running, kicking and handling skills, as well as tactics and set plays, to break the defensive line, instead of brute force . Generally forwards do the majority of the work (hit - ups / tackling). </P> <Ul> <Li> The title of fullback (numbered 1) comes from the fullback's defensive position where the player drops out of the defensive line to cover the rear from kicks and runners breaking the line . They therefore usually are good ball catchers and clinical tacklers . In attack the fullback will typically make runs into the attack or support a runner in anticipation of a pass out of the tackle . Fullbacks can play a role in attack similar to a halfback or five - eighth and the fact that the fullback does not have to defend in the first defensive line means that a coach can keep a playmaker from the tackling responsibilities of the first line whilst allowing them to retain their attacking role . </Li> <Li> The wingers (numbered 2 and 5) are normally the fastest players in a team and play on the far left and right fringes of the field (the wings). Their main task is to receive passes and score tries . The wingers also drop back on the last tackle to cover the left and right sides of the field for kicks while the fullback covers the middle . </Li> <Li> The centres (numbered 3 and 4) are positioned one in from the wings and together complete what is known as the three - quarter line . Usually the best mixture of power and vision, their main role is to try to create attacking opportunities for their team and defend against those of the opposition . Along with the wingers, the centres score plenty of tries throughout a season . They usually have a large build and therefore can often play in the second row forwards . </Li> </Ul> <Li> The title of fullback (numbered 1) comes from the fullback's defensive position where the player drops out of the defensive line to cover the rear from kicks and runners breaking the line . They therefore usually are good ball catchers and clinical tacklers . In attack the fullback will typically make runs into the attack or support a runner in anticipation of a pass out of the tackle . Fullbacks can play a role in attack similar to a halfback or five - eighth and the fact that the fullback does not have to defend in the first defensive line means that a coach can keep a playmaker from the tackling responsibilities of the first line whilst allowing them to retain their attacking role . </Li>

When did rugby league became a summer sport