Jimmy Garoppolo has likely been staring at Kyle Shanahan’s playbook non-stop since Bill Belichick sent him to the San Francisco 49ers. He has an entirely new language to learn and, while he has a bit of a rosetta stone in that he’s played NFL football, he still needs to spend a lot of time decoding.
Bill Belichick uses the Erhardt-Perkins system of terminology to build his plays. In this system, plays are organized and referred to by their concept. Rather than using the Air Coryell numbering system to detail each receiver’s route, Belichick can get a one word call in that tells both QB and receivers what concept to run.