Running out the clock
In American football, each quarter of a game is measured with a 15-minute game clock, or 12-minute clock in many high school football codes and the German Football League. A team in possession of the lead and the ball will attempt to use up as much of the game clock as possible in order to bring the game to an end more quickly, thus denying the opposition another chance on offense.
Quarterback
As late as the 1960s, running plays occurred more frequently than passes. NFL quarterback Milt Plum later stated that during his career (1957-1969) passes typically only occurred on third downs and sometimes on first downs. Quarterbacks only increased in importance as rules changed to favor passing and higher scoring and as football gained popularity on television after the 1958 NFL Championship Game, often referred to as "The Greatest Game Ever Played". Early modern offenses evolved around the quarterback as a passing threat, boosted by rules changes in 1978 and 1979 that made it a penalty for defensive backs to interfere with receivers downfield and allowed offensive linemen to pass-block using their arms and open hands; the rules had limited them to blocking with their hands held to their chests. Average passing yards per game rose from 283.3 in 1977 to 408.7 in 1979.
The NFL continues to be a pass-heavy league, in part due to further rule changes that prescribed harsher penalties for hitting the quarterback and for hitting defenseless receivers as they awaited passes. Passing in wide-open offenses has also been an emphasis at the high school and college levels, and professional coaches have devised schemes to fit the talents of new generations of quarterbacks.