My rough (approximately) zero-sum approach to keeping the defense intact:
I. Players currently under contract:
1. Darrelle Revis, CB. Signed through 2015. 2015 cap hit: $25M (including $5M carryover from 2014).
2. Jerod Mayo, LB. Signed through 2017. 2015 cap hit: $10.3M.
3. Vince Wilfork, DT. Signed through 2016. 2015 cap hit: $8.4M.
4. Brandon Browner, CB. Signed through 2016. 2015 cap hit: $4.9M.
5. Kyle Arrington, CB. Signed through 2016. 2015 cap hit: $4.6M.
6. Rob Ninkovich, DE/OLB. Signed through 2016. 2015 cap hit: $3.7M.
7. Chandler Jones, DE. Signed through 2016, with an option for 2017. 2015 cap hit: $2.6M.
8. Dont'a Hightower, LB/DE. Signed through 2016, with an option for 2017. 2015 cap hit: $2.5M.
9. Dominique Easley, DT/DE. Signed through 2017, with an option for 2018. 2015 cap hit: $1.7M.
10. Alfonzo Dennard, CB. Signed through 2015. 2015 cap hit: $1.5M.
11. Tavon Wilson, S. Signed through 2015. 2015 cap hit: $1.3M.
12. Jamie Collins, LB. Signed through 2016. 2015 cap hit: $1,0M.
13. Logan Ryan, CB/S. Signed through 2016. 2015 cap hit: $750K.
14. Duron Harmon, FS. Signed through 2016. 2015 cap hit: $725K.
15. Nate Ebner, S. Signed through 2015. 2015 cap hitL $685K.
16. Michael Buchanan, DE/OLB. Signed through 2016. 2015 cap hit: $600K.
17. Chris Jones, DT/DE. Signed through 2016. 2015 cap hit: $585K.
18. Zach Moore, DE. Signed through 2017. 2015 cap hit: $535K.
19. Malcolm Butler, CB. Signed through 2016. 2015 cap hit: $510K.
19 players under contract; total 2015 cap hit = $71.89M.
II. FAs
20. Devin McCourty, FS
21. Akeem Ayers, DE/OLB
22. Pat Chung, SS
23. Alan Branch, DT
24. Jonathan Casillas, LB
25. Sealver Siliga, DT (ERFA)
III. Proposed extensions/signings:
Cap Savings from Extensions/Restructurings:
1. Extend Darrelle Revis: 4 years/$60M, $45M guaranteed, $20M signing bonus. That's a higher AAV than Joe Haden, Richard Sherman or Patrick Peterson, with more guaranteed money than Haden or Sherman and a bigger signing bonus than any of them. It's above the AAV for the top CBs, and bit below the AAV for the top 3 defensive contracts in the NFL (JJ Watt $16,5M AAV; Mario Williams $16M AAV; Gerald McCoy $15.8M AAV). Base salaries + incentives of roughly $7M, $9M, $9M and $15M (the last year non-guaranteed). 2015 cap hit: $17M ($5 million pro-rated signing bonus + $7M base + $5M carryover from 2014). Net 2015 cap savings: $8M. MgTeich and others have suggested more aggressive savings proposals, but I'm being conservative.
2. Restructure Jerod Mayo's deal to lower his 2015 cap his to about $7.5M. Net 2015 cap savings: $2.8M. Not sure if this would be via a direct pay cut, a restructuring, or an extension, but I think there is some room to work here.
3. Extend Kyle Arrington through 2017 with a 1 year $4M extension, lowering his 2015 cap hit by $1M.
4. Extend Brandon Browner through 2017 with a 1 year $4M extension, lowering his 2015 cap hit by $1M.
Total 2015 cap savings from defensive restructurings/extensions: $12.8M.
Cap Additions from Extensions/Re-Signings:
4. Sign Devin McCourty to a 5 year/$40M extension with $16M guaranteed and a $10M signing bonus. Base salary+incentives of $2.5M, $5.5M, $6.5M, $6.5M and $9M. 2015 cap hit: $5M.
5. Sign Akeem Ayers to a 4 year/$16M extension with $7.5M guaranteed and a $6.5M signing bonus. Essentially the same deal that Kyle Arrington got in 2013. Base salaries+incentives of $1M, $2M, $3M and $3.5M. 2015 cap hit: $2.625M. Someone could possibly throw more money at Ayers if he chooses to hit FA, but he's had only half a season of productivity and was on the scrap heap fairly recently, so I'm not sure he gets silly money. This deal values him - like Arrington - as a major rotational player and part of the defense, with starting potential.
6. Sign Alan Branch to a 2 year / $3M contract with $1M guaranteed and a $1M signing bonus. Base salary+incentives of $1M in 2015 and 2016. 2015 cap hit: $1.5M.
7. Sign Patrick Chung to a 2 year / $4M contract with $2M guaranteed and a $1M signing bonus. Base salary+incentives of $1.3M and $1.7M. 2015 cap hit: $1.8M.
8. Sign Jonathan Casillas to a 3 year/$4.5M contract with $2M guaranteed and a $1M signing bonus. Base salary+incentives of $1M, $1M and $1.5M. 2015 cap hit of $1.333M.
9. Sign Sealver Siliga to an ERFA contract. 2015 cap hit of around $660K, per Miguel.
Total 2015 defensive extensions/resignings: $12.918M.
That's about a $100K difference, which is minimal, and could probably be made up elsewhere.
These are very crude numbers, and rough estimates. Obviously, any of the re-signings could be drastically altered if someone wants to break the bank. But I think they are reasonable starting points. I think it is possible - though by no means easy, or a given - to keep the defense intact without adding to our current 2015 defensive cap allocation.
This would allow the Pats to potentially retain the 2014 defensive core completely intact for 2015, while keeping their cap space and carryover from 2015 for re-signing offensive and ST players, and for the draft, UDFAs, and contingency funds.
Wilfork's deal will likely be off the books in 2016, providing room for one of the 5th year options on Jones/Hightower. The other can probably be managed with the projected cap growth. Managing extensions for all of Jones, Hightower and Collins will be tricky, but with work the Pats should be able to keep the defense largely intact through 2017.