When constructing a secondary, it's not so much about having your best 2 Cornerbacks and best 2 Safteys on the field, but rather your best 4 Defensive Backs playing together in a complimentary manner.
Our top 4 Defensive Backs are McCourty, Talib, Dennard, and then one of Chung/Gregory/Wilson.
Once Aqib Talib is eligible for games, he immediately becomes out best Cornerback. His strengths lie in his size, range, and ability to jam receivers and play man coverage. When choosing a player to start across Talib, you would like a player who offers a similar style of play. Alfonzo Dennard offers that, and he has been on the rise these past few weeks and I believe his play has warranted a starting position.
McCourty was our best Cornerback - before this trade - yet still may be our best overall Defensive Back. He struggles in man coverage yet excels in zone coverage, and has all the traits of a prototypical Free Safety. We have to remember, the coaches WANTED to move McCourty to Safety permanently this year, but they didn't trust in the other Cornerbacks enough to take away his presence. Now, Talib is in Foxborough. Dennard has established himself. And with the continuous struggles at Safety and the continuous death by 50 yard passes, McCourty can finally "go home."
There is a lot of praise for Wilson, but mind you, his rookie mistakes have cost us a game and has made us susceptible to the deep ball. I like Wilson as the "Money" player, it's a good role for him at this point in his career. That would leave Gregory and Chung as options to play alongside McCourty. What I think the coaches will do is rotate these players depending on situation. Expecting the pass? McCourty-Gregory. Need to make a stand against the run? McCourty-Chung.
The Patriots haven't really been playing the traditional Free Safety/Strong Safety positions as much as Left Safety/Right Safety. McCourty is well rounded in both pass defense and run defense, and rotating a player who specializes in either or next to him could pay off.
Therefore, the Patriots new-look secondary would be:
LCB: Alfonzo Dennard (In my observations, Dennard has played better when aligned as the LCB).
RCB: Aqib Talib (He can play any CB position, LCB, RCB, SCB).
LS: Devin McCourty (Has been groomed on the left side his whole career).
RS: Gregory/Chung (Pass: Gregory, Run: Chung)
SCB: Kyle Arrington
Dime: Tavon Wilson.
