After being measured, the game balls will be secured and withdrawn from play. Back-up footballs will be utilized for each team during the second half of these randomly chosen games only. The replacement ball will be inflated to the same pressure as the original ball.
The used ball will be discarded after any score is established or at the end of the game. However, coaches can decide to throw out a ball that is damaged through use. This would include balls that are deflated, have cuts or scratches on them, or appear to no longer be in good condition.
Coaches must ensure that there is at least one ball available for each series of downs during both regular season and post-season play. If not, then players will not have enough opportunity to take advantage of defensive mistakes. In addition, coaches should keep in mind the importance of rotation when planning their strategy for game time utilization. For example, if several players are likely to get injured if they continue to run on a fatigued muscle group, then it makes sense to use some of those opportunities to give other players on the roster a chance to see action.
During pre-season games, it is common practice for coaches to use a different color jersey for each offensive player.
The NFL delivers around 30 balls to each club the week before each game; these are the quarterback balls. The equipment people are permitted to break them in (within reason—the NFL doesn't want really beat up footballs showing on TV) to the quarterbacks' standards. Then they're ready to go for use in games.
During games, if a ball is deemed by a referee to be defective (i.e., not new or not properly inflated), then it can be replaced by using one of the two options available to teams during timeouts. If a team chooses to do this, then an additional ball must be obtained from the league office. As soon as a replacement ball is received by a quarterback, he may continue playing with it until he receives another warning from the referee that the ball has been replaced. If a second warning is given, then the quarterback will be penalized 15 yards and his team will have a second chance to replace the deflated ball. A third infraction results in disqualification.
Teams are allowed three timeouts per game, which can be used at any time during the play clock. If a team uses all three of its timeouts before the end of the first quarter, then it will receive a one-quarter penalty against it. If after three timeouts have been awarded, a team does not use one of them before the end of the half, then it will forfeit the remainder of the quarter.
The game is separated into 15-minute quarters, with a big break after 30 minutes, known as half time. The players simply trade sides at the end of the first and third quarters. The ball is transferred to the matching position on the other side of the field, and the game resumes. This method was adopted by most professional sports leagues, but it is not used by any school that plays Division I football.
In fact, no major university or College in the United States plays football on campus anymore. The last such game was played in December 2006 between Miami (Ohio) and Ohio State. The game was called because of rain delays that lasted more than two hours.
However, many smaller schools still play a spring game around Easter weekend. A few remain loyal to the old style of football where players would stay on their own side of the field while heaving the ball downfield during practice sessions. These games are often won by the team that executes the playbook best. However, there are also many that are now scripted affairs where each player is given a specific role on offense or defense before the season starts. These games usually have a strong effect on the depth charts for the following year's team.
Also, some small colleges continue to play a game called "fish" on Halloween night. This is similar to how early football games were played until the 1950s when it became too dangerous to play the game without a referee.