Watching film has always been a crucial part of NFL players' preparation. They need to learn their rivals' tendencies, how to react and break down their schemes in real-time, what to expect and how to beat their coverages, and never-ending etcetera.
That's why some of the best to ever do it happens to be some guys obsessed with breaking down film and getting to know their rivals as well as their own playbook. And Peyton Manning was one of those guys.