The impact of strength varies by position in football. However, all football players benefit from being stronger than other players at the same position, as well as other players they compete against. The NFL combine for rookie prospects includes a bench press test so that teams can evaluate player strength.
Strength is most important on the offensive and defensive lines where the primary role of players is to fight for position at the line of scrimmage. Strength enables quarterbacks, running backs and wide receivers to fend off tacklers and gain more yardage. Tackling is an important role for all defensive players, so strength is also essential in those positions.