Over those four games, I'd expect the Pats to perform one game worse with Garoppolo than Brady. With Brady, I think they'd go either 4-0 or 3-1. With Garoppolo, either 3-1 or 2-2. That change in QBs obviously moves the needle in any game, but it only dramatically swings my expectations against Arizona. If Garoppolo is our QB week 1, I expect the Pats to lose.
The Cardinals are an elite team, but the Dolphins and Bills look awful. Neither game's a gimme just because division games never are, but I'd expect the Pats to win both of them regardless of who's the QB. And the Texans don't scare me at all either. Historically, it's a matchup that really works in the Pats' favor, and we're lucky to be playing them early in the season before injuries have take their toll and before Osweiler (who I don't think is very good anyway) gets too comfortable in that offense. The Pats have historically done a very good job of managing Watt, and they'll play McCourty over the top of Hopkins all game. Add in that Hopkins is the type of WR that our corners tend to hold up pretty well against, and I just don't feel very threatened by Houston in general. With Brady, I think we reliably win by 2+ TDs.