reason by their coach – typically because of injury, to manage fatigue, for tactical reasons or due to poor performance. Under current rules, players who have been substituted are typically allowed to be substituted back into the game later on. Leagues in different countries have had different rules on how many interchanges can be made in a game. the Super League allowed up to ten interchanges per team in each game, this was reduced to eight interchanges per team per game, commencing in the 2019 season. Commencing in the 2016 season, Australia's National Rugby League permits up to eight interchanges per team per game. Additionally, if a player is injured due to foul play and an opposition player is has been sin-binned or sent off then the injured player's team is given a free interchange. Often an interchange bench will include at least one (and usually two) replacement props, as it is generally considered to be the most physically taxing position and these players are likely to tire the quickest. Concussion substitute Commencing in 2021, a player named as the squad's 18th player on match day is able to take the field when three players fail a head injury assessment; or when a player suffers a match-ending injury caused by foul play, in which the opposing player was either sin-binned or sent off. Since the change, there have been calls to reduce the number of players that suffer a match-ending injury to two players, in the wake of a few incidents in the NRL. The concussion substitute was used during the 2021 Rugby League World Cup played in 2022, and adopted by the RFL in 2023. Roles As well as their positions, players' roles may be referred to by a range of other terms. Marker Following a tackle, the defending team may position two players – known as markers – at the play-the-ball to stand, one behind the other facing the tackled player and the attacking team's dummy-half. Dummy half The dummy half or (acting half-back) is the player who stands behind the play-the-ball and collects the ball, before passing, running or kicking the ball. The hooker has become almost synonymous with the dummy half role. However, any player of any position can play the role at any time and this often happens during a game, particularly when the hooker is the player tackled. First receiver The first receiver is