In 1987, each side was allowed two replacements in a single game (one goalkeeper and one outfield player). In the 1994-95 season, this was expanded to three, however one of them had to be a goalie. After one season, the three substitutes can be deployed for whatever purpose they want. They can be used entirely differently if their manager thinks it will benefit his side.
The rule is that each substitute must come from outside the squad. This is to prevent any of the other teams' players who are not included in the original list of 21 opponents (or 22 if you include the coach) from being replaced by more fresh players after seeing how they are expected to be used.
There have been cases where a club has had enough of its players being injured and wants to give some of the younger ones a chance. So it calls up some reserves from its own youth system or abroad. Such replacements are not classed as substitutes but honorary members of the squad.
The only time when an extra player who is not a substitute can play in a match is if he is a guest player. A guest player is someone who has been invited to play for the team but who isn't registered with a professional club. For example, a famous footballer who has retired but wishes to help his former team out by playing in a match would be considered a guest player.
The regulations were not amended until 1987 to allow for a second substitution. This proved to be the thin end of the wedge, with rule modifications ranging from allowing two outfield subs plus a goalkeeper to the present situation of allowing up to three of seven nominated substitutes to be utilized in the Premier and Football Leagues. The Premier League is the only major league left using just one substitute.
The first substitution in international soccer was introduced in the 1954 World Cup between Germany and Sweden. The German team had taken a 3-0 lead into the break but then went down 3-1 to Sweden. After the loss, Germany's coach said his side needed more time to recover after their exhausting campaign. The Germans would go on to lose the final match 3-1 to Brazil. Since then, substitution patterns have changed over time as well as across national borders.
In modern soccer, any player who has gone off injured or fatigued can be replaced by another player on the field of play. This replacement player does not have to be substituted himself/herself; a substitute may also be sent off to make way for another player. If a player is dismissed for serious foul play or violence towards opponents, he/she will usually receive a suspension, with or without pay. When this happens, a replacement player will come onto the field (either a current player or a member of the coaching staff) in order to give his/her team a chance of winning the game.
In soccer, how many replacements can be used? Typically, seven replacements, generally including one goalie, are named on the bench at the start of a professional game. The competition regulations will define how many players other than the starting 11 may be named to the matchday squad.
In general, four substitutes are used in major competitions such as the UEFA Champions League and Europa League. In lower-ranked games, only three substitutes are often allowed. Replacements are usually chosen by the manager or coach, but they can also be selected by other members of the coaching staff or even by fans via text message or social networking site. They can come onto the field during injury time or in the case of a replay.
The number of substitutions made in a game depends on several factors such as the type of game (i.e., competitive or exhibition), the level of the sport, and the preferences of the manager or coach. Generally, more substitutions are made in exhibitions than in competitive games. At the professional level, managers tend to make fewer substitutions because they believe that they have enough talent on the field to win or lose the game. However, if they feel that they cannot compete with an opponent that makes more substitutions, they might change their strategy and use all their replacements.
At the youth level, coaches often allow their players to play for longer periods of time without replacing them.
"Up to a maximum of three substitutions may be employed in any match played in an official tournament organized under the auspices of FIFA, the confederations, or the member associations," according to the Laws of the Game. In addition, up to six substitutions may be employed in national A team matches.
Substitutions are useful in several situations. For example, if a player is injured and has to leave the field, a replacement can take his place. If a player is sent off the field, he can be replaced. Last, but not least, a coach may want to make some changes during a game for whatever reason.
According to the Laws of the Game, each substitution must be requested by the captain of the team making them. He can do this from the sideline or from the changing room before coming back on to the field.
There is no limit to the number of substitutes that can be used by each team in a single match. However, they must all be notified about their availability before the start of the game. Teams are allowed to have an unlimited number of substitute players on the field at one time as long as they notify the referee before each play.
In practice, most teams use only two or three subs. This is because there are only so many healthy players on the field at one time and adding more would just cause confusion.