<P> Free substitution is a rule in some sports that allows players to enter and leave the game for other players many times during the course of the game; and for coaches to bring in and take out players an unlimited number of times . </P> <Ul> <Li> Basketball . Basketball allows unlimited substitution of players at dead balls, such as full times - out, out - of - bounds turnovers and fouls . Players are allowed to go out and come in again many times, unless they are disqualified or ejected . Players are often substituted for, since it is physically difficult to play an entire basketball game (40 minutes in most competitions, 48 in the NBA). Substitutions are also made if a player is getting too many personal fouls and is in danger of disqualification . </Li> <Li> Gridiron football . Players can be changed during any dead ball situation . Most college and pro football teams use 11 completely different players on offense and defense . Often, substitution is made depending on the play being run; for example, a team might bring in a fullback or tailback for a rushing play, or several wide receivers for a passing play . There are also major substitutions made for special teams plays such as punting or kicking a field goal . (Historically, this was not the case; gridiron - based codes originally had a one - platoon system in place that required all players to play all phases of the game . The one - platoon system was largely abolished in the 1940s but aspects of it remained in force in college football until the 1960s, at which time total free substitution was implemented .) </Li> <Li> Ice hockey . Players can be substituted for at any point in the game, even when the puck is in play . The only exception is that if a team ices the puck they may not make any changes until after the ensuing faceoff . Almost all professional hockey teams use up to four lines of forwards and three pairings of defensemen in rotation during any given game . </Li> </Ul> <Li> Basketball . Basketball allows unlimited substitution of players at dead balls, such as full times - out, out - of - bounds turnovers and fouls . Players are allowed to go out and come in again many times, unless they are disqualified or ejected . Players are often substituted for, since it is physically difficult to play an entire basketball game (40 minutes in most competitions, 48 in the NBA). Substitutions are also made if a player is getting too many personal fouls and is in danger of disqualification . </Li> <Li> Gridiron football . Players can be changed during any dead ball situation . Most college and pro football teams use 11 completely different players on offense and defense . Often, substitution is made depending on the play being run; for example, a team might bring in a fullback or tailback for a rushing play, or several wide receivers for a passing play . There are also major substitutions made for special teams plays such as punting or kicking a field goal . (Historically, this was not the case; gridiron - based codes originally had a one - platoon system in place that required all players to play all phases of the game . The one - platoon system was largely abolished in the 1940s but aspects of it remained in force in college football until the 1960s, at which time total free substitution was implemented .) </Li>

When can a player be substituted in basketball
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