The first thing to get out of the way is to accept that Jimmy Garoppolo isn't Tom Brady. He doesn't have 14 years of experience under his belt to rely on, but he does have a head coach with 41 years of experience in the NFL to consult. The good news for Garoppolo is he will have most of the Patriots weapons from their starting offense. He will get to throw to Rob Gronkowski, Martellus Bennett, Julian Edelman, and Chris Hogan on primarily every down. The running back spot will cycle between LeGarrette Blount and James White, depending on the situation.
In order to make sure Garoppolo doesn't get overwhelmed, the Patriots are going to have to include things that he is comfortable with. Against the Saints and Bears, Garoppolo looked very comfortable in the up-tempo 2-minute offense with a touchdown drive in each game. Garoppolo comes out of an offense at Eastern Illinois that was mostly up-tempo, shotgun spread. Pushing the tempo in the game allows for Jimmy to develop a rhythm and keep the opposing defenses on their heels. Even though Garoppolo will be facing four tough defenses to start the season, they have a common weakness: linebacker coverage.
The Patriots running backs need to carry the load for the offense, which means LeGarrette Blount needs to be ultra-effective if the defense counters the Patriots 12 personnel with a nickel defense. If the opponent counters in base, the play needs to change to spread out the tight ends and force the linebackers to cover in space. If they're having to chase down White, Gronk, and Marty B, that makes them more tired in the running game and more susceptible to Blount Force. Blount while he isn't a great RB, he is a solid efficiency runner which is why the team has kept him despite the fact the fans keep calling for his head.
The way the Patriots offense is designed, they use formations to force the defense to declare man or zone coverage. Depending on what coverage they get, the route changes. If the opposing defense is in zone, the routes change to what beats that particular zone. If it's a Cover 3, the slot and the inline TE may be running dual seam routes to attack the holes between the deep safety and the two boundary corners. That's just one example out of the playbook. If the defense declares man, the Patriots use motions to force defenders to back off press coverage or if it's an obvious mismatch (i.e. Gronk vs. a linebacker in single coverage) they attack it.
For Jimmy G, the biggest three things he needs to know is when it's time to cut your losses on a busted play, counting defenders in the box and knowing when to change out of a run call, and the understanding of the difference between man and zone coverage. A key player in forcing the defense to tip their coverage is Gronk, especially if flexed out wide as a split-end since he's virtually impossible to cover with just one player. While Jimmy isn't going to process the game as fast as Brady, he should have at least picked up a lot of the nuances needed to sustain the Patriots offense. While I'm not drafting Jimmy G on my fantasy team, I think he'll do alright.