In the past, the team operated out of the nickel and dime ~70% of the time. Historically, where they have been burned is coverage by the CB and in the middle of the field via the TE. To me, it's been a gradual improvement..
2011- McCourty goes to FS to cover the deep ball and Arrington covers the slot. The pass rush is better.
2012- Talib gives them a good cover corner. Dennard is added to the mix. The pass rush improves.
2013- McCourty, Dennard, Talib are a good combo. Ryan and Harmon are added. The pass rush is ok but still not potent. Collins brings speed and coverage abilities to the middle of the field and on the TE.
2014- Add Revis (which is an upgrade over Talib) and Browner to cover the larger receivers (with Collins)in the mid-level passing game.
By the middle of the season, with Browner, the second year players really getting it and the other newcomers getting more and more comfortable in the system, this will be a top 5 defense. I am convinced of this. Way too much talent on the field and in the coaching staff to be porous ala 2010.
There may be match problems here and there but I feel that the Pats finally have the cover guys to at least be competitive.