Section 4: Players & Officials
Composition of teams (Rule 2). A maximum of eleven players from each team take part in play at any particular time (Rule 2.1). Per the Rules' Terminology definitions, a team consists of a maximum of sixteen persons, composed of a maximum of eleven players on the field and up to five substitutes; this may be amended by Regulation to a maximum of eighteen players. Each team fields either a goalkeeper with full protective equipment or plays entirely with field players and no goalkeeping privileges (Rule 2.2); any change between these options must take place as a substitution.
Substitutions (Rule 2.3). Substitution is permitted at any time except within the period from the award of a penalty corner until it has been completed, during which substitution is permitted only for an injured or suspended defending goalkeeper. There is no limit on the number of players substituted at one time or the number of times a player may be substituted, but a substitution only takes effect after the outgoing player has left the field, and field players must enter or leave within 3 metres of the centre-line on a side agreed with the umpires. Time is stopped for any substitution involving a goalkeeper but not for other substitutions.
Captains (Rule 3). One player of each team must be appointed captain, with a replacement captain appointed if the captain is suspended. Captains are responsible for the behaviour of all players on their team and for ensuring substitutions are carried out correctly; a personal penalty is awarded if a captain fails to exercise these responsibilities.
Umpires (Rule 11). Two umpires control the match, apply the Rules, and are the judges of fair play. Each umpire has primary responsibility for decisions in one half of the field for the duration of the match, including free hits, penalty corners, penalty strokes, and goals awarded in that half. Umpires are responsible for keeping a record of goals scored and of warning or suspension cards used, and for ensuring the full time is played. Umpires blow the whistle to start and end quarters, start a bully, enforce a penalty, stop and re-start time around a penalty corner, start and end a penalty stroke, and indicate goals; umpires must not coach during a match (Rule 11.6-11.7).