Modernization and innovation (1906–1930)

As a result of the 1905–1906 reforms, mass formation plays became illegal and forward passes legal. Another important change, formally adopted in 1910, was the requirement that at least seven offensive players be on the line of scrimmage at the time of the snap, greatly reducing the potential for collision injuries. Several coaches emerged who took advantage of these sweeping changes. Amos Alonzo Stagg introduced such innovations as the huddle, the tackling dummy, and the pre-snap shift. Other coaches, such as Pop Warner and Knute Rockne, introduced new strategies that still remain part of the game. Besides these coaching innovations, several rules changes during the first third of the twentieth century had a profound impact on the game, mostly in opening up the passing game. In 1914, the first roughing-the-passer penalty was implemented. In 1918, the rules on eligible receivers were loosened to allow eligible players to catch the ball anywhere on the field—previously strict rules were in place only allowing passes to certain areas of the field. Scoring rules also changed during this time: field goals were lowered to three points in 1909 and

touchdowns raised to six points in 1912.

Star players that emerged in the early twentieth century include Jim Thorpe, Red Grange, and Bronko Nagurski; these three made the transition to the fledgling NFL and helped turn it into a successful league. Sportswriter Grantland Rice helped popularize the sport with his poetic descriptions of games and colorful nicknames for the game's biggest players, including Grange, whom he dubbed "The Galloping Ghost," Notre Dame's "Four Horsemen" backfield, and Fordham University's linemen, known as the "Seven Blocks of Granite Pop Warner Glenn "Pop" Warner coached at several schools throughout his career, including the University of Georgia, Cornell University, University of Pittsburgh, Stanford University, and the Temple University One of his most famous stints was at the Carlisle Indian Industrial School, where he coached Jim Thorpe, who went on to become the first president of the National Football League, an Olympic Gold Medalist, and is widely considered one of the best overall athletes in history. Warner wrote one of the first important books of football strategy, Football for Coaches and Players, published in 1927. Though the shift was invented by Stagg, Warner's single wing and double wing formations greatly improved upon it; for almost 40 years, these were among the most important formations in football. As part of his single and double wing formations, Warner was one of the first coaches to effectively utilize the forward pass. Among his other innovations are modern blocking schemes, the three-point stance, and the reverse play. The youth football league, Pop Warner Little Scholars, was named in his honor.