I'll copy and paste a comment I made from one of my Browns forums earlier today, because it seems relevant.....
First off, let me just say that Brady's accomplishments speak for themselves. He's truly a great QB, and you can't ignore all the championships and stats and awards. But I truly believe that's mostly due to Belichick and the "Patriot Way" that he built. Much of Brady's greatness is just a product of the system. Hell, Brady's own coaches believed it......
"One New England assistant said the general feeling among staff members around that time wasn't that Belichick's system could make Super Bowl quarterbacks out of all 32 NFL starters. "But if you gave us any of the top 15, we could do it," the assistant said. "I don't think the coaches view Tom as special as everyone else in football does. Mr. Kraft thinks Tom is the greatest gift ever, but the coaches don't."
This article is couple years old now, but relevant....
Patriots quarterback Tom Brady felt trapped in the offseason and was not sure he wanted to play anymore for the only NFL coach he has ever had, Bill Belichick, according to a new book on Belichick's life.
www.espn.com
Need some actual proof? Well, remember the time Brady was lost for the year, and they still went 11-5 with Matt freakin' Cassel, who at that point hadn't even played since high school? He had no NFL experience, and was a backup in college. He ended up being a journeyman QB for the rest of his career. But Belichick's system made him look like a winner the one year he played in New England. When most good teams lose their star QB, their season is lost. Not the case for the Patriots.
Still think I'm crazy? Well, bear with me. Just watch Brady play, study his game. Yes, he's smart. Yes, he's accurate. He has a ton of quality traits that are hard to find. Yes, he's a really good QB! But notice the clean pocket, notice the quick throws to open receivers. Notice how he never takes a hit. OK, now watch the bad games from any point in Brady's career. Notice a common theme? Pressure up the middle disrupting the pocket. Taking hits/sacks because he can't avoid the pressure, can't bail out of the pocket, can't extend the play with his legs. Get in his face and he becomes completely ineffective.
Think about that for a minute. How many times have you seen Brady evade pressure, roll out, throw on the run and complete a pass downfield? You can count on one hand the times he'll do that over the course of a season. Guys like Russell Wilson and Aaron Rodgers do that multiple times every drive!
That's why I say Brady is a system QB. He's lucky enough that he ended up in the perfect system to suit his strengths, with the perfect organization. But you can't just plug him in on any team and expect him to make a difference. Doesn't Tampa/Arians like to go vertical? To hit the big play downfield, he absolutely needs time to throw because he can't "create" on his own. He needs a good line, a clean pocket, a quick hitting passing attack to get the ball out quick without getting touched. He needs a smart coaching staff, and smart players around him. How many NFL teams can offer all of that?
I'm not trying to crap on him or say he isn't a great QB, I'm just stating why I think he's overrated compared to some of the other great QB's, and why it's a big mistake to leave New England.