Putting together the playbook


"Adventure is just bad planning." - Roald Dahl

When do the Cowboys OC, head coach, and I'm guessing Dak Prescott put together the playbook and plays? Are they pretty much just taking last years playbook and adding some new wrinkles or do they start from scratch each year? How much do they add in once they season starts? I figured other than the bye week they can't add too much new stuff.