It's happening.
Brady is still a great QB, but he is now a great QB who is 38 years old. The Patriots have drafted like **** for a while now and they lack anything resembling talent on offense, save for a one-legged Rob Gronkowski. On defense, they have a good secondary, a shell of a Vince Wilfork, and a bunch of try-hard guys who are coached well.
I don't know what's going to happen the rest of this season, but Miami was simply a better football team than the Patriots on Sunday. It was not an 'any given Sunday' win. It was a 'we're just better than you' win. That should be real scary for Patriots fans, because Miami hasn't had a win like that against New England in almost 20 years.