The why is everything. That’s the ethos of Kyle Shanahan, son of a coaching legend and now the leading figure in a revolution that is sweeping the league. Shanahan and the branches of his coaching “tree”—including Sean McVay, Mike McDaniel, Raheem Morris, and Matt LaFleur—came up in a martial sport where coaches and players did things a certain way for the simple reason that coaches and players had always done them that way. In the early 2010s, while working for the Washington Redskins, Shanahan and the others began to ask why, and in the process threw out decades of accumulated tradition in favor of unorthodox—and wildly successful—new schemes. Today, these innovative coaches have helped propel the NFL to new heights of viewership and drama. With extensive access, acclaimed reporter Michael Silver presents a story of close friendship and intense rivalry—a story that happens to be the story of modern football.