To begin a game, a team must have five players. If all but four players foul out, you can then play with four, three, two, or one. On the court, you must have four players. The sole exception is when a player gets injured or fouls out. At that point, you can use three players without having to replace them. An NBA team consists of nine players on the court at any given time. A player can be in jail sentence, hospitalized, or otherwise unable to play and the team can continue to compete. A team's ability to play with less than its normal roster size is called "playing small". These smaller teams are usually more competitive because they have more opportunities to win or lose games. Playing small is useful for many reasons: it gives your other players opportunities to prove themselves; it gives you extra depth; and finally, it reduces the risk of injury. The downside is that these smaller teams tend to be harder to defend since there are only so many positions on the court where you can put people who aren't playing basketball. Almost every NBA team can play with less than its normal roster size during a regular season game.