In the sport of Australian rules football, each of the eighteen players in a team is assigned to a particular named position on the field of play. These positions describe both the player's main role and by implication their location on the ground. As the game has evolved, tactics and team formations have changed, and the names of the positions and the duties involved have evolved too. There are 18 positions in Australian rules football, not including four (sometimes 6–8) interchange players who may replace another player on the ground at any time during play.
The fluid nature of the modern game means the positions in football are not as formally defined as in sports such as rugby or American football. Even so, most players will play in a limited range of positions throughout their career, as each position requires a particular set of skills. Footballers who are able to play comfortably in numerous positions are referred to as utility players.
In an effort to maintain traditional positions, at the beginning of each quarter and after each goal each team must have a maximum of 6 players in each 50m arc, including 1 in the goal square. Each team are also restricted to a maximum of 4 within the centre square, including 1 in the centre circle. If this is breached, a free kick is awarded.[1]