Hey, so I was browsing your site and read Dawn's article "Super Bowl 2014: Will Dallas Follow The Seahawks Model?" and the comments following. I started to type a comment there, but it got pretty long so a fanpost it is. I wanted to address some of the questions brought up in the comments.
First, I couldn't even begin to give the full breakdown of Seattle's D, how/why it works, etc. Field Gulls has a treasure trove of full (and exhaustive) breakdowns of Pete Carroll's defense.
FG Editor Danny Kelly explaining the Seahawks defensive philosophy.
Link to a series of articles from mid-2013 explaining the "4-3 personnel with 3-4 principles" system.
To try and answer some of the items brought up in the comments:
* Seattle's drafting (late-round hits, etc.): Pete Carroll and John Schneider (Seahawks GM) look for specific traits to their players, damn the conventional wisdom. Bruce Irvin was drafted to be a LEO, so we'll take him 15th overall even if no one else had him in the first. Our cornerbacks all HAVE to be tall and physical. The shortest CB on our roster is 5'11" (Walter Thurmond), and I think he was a value pick - he fell to the 4th round in 2010 due to a torn ACL his senior year. But they're all taught to play the same physical way so if one goes down (Browner) another one steps in with little drop off (Maxwell). They are "indoctrinated into the system," as Carroll has said.
* How well would Claiborne and Carr if they were Seahawks, or how well would Maxwell do as a Cowboy? Sorry, I haven't seen enough Dallas games to answer that. I will say that scheme matters - a lot. You can't just take good corners, plug and play them in any system and expect the same results. (Remember Philly's Dream Team secondary of DRC, Nnamdi, and Asante? That's what happens when the system doesn't match the talent.)
Along those lines, Earl Thomas is really what holds this defense together. Without his ridiculous range, we couldn't use "Deathbacker" Kam Chancellor in run support laying wood on WRs (Hi Demaryius Thomas) and TEs (Hi Vernon Davis).
* Pass rush was a big priority last offseason. Last year we really only had one true pass rushing threat in Chris Clemons, and when that joke of a field in DC ate his ACL it cost us against Atlanta. So we pushed hard for one of Avril/Bennett - and got both(!) We also churned the FA wire to get crucial rotational bodies like Tony McDaniel and Clinton McDonald.
* We could afford Avril, Bennett, and Percy because we hit on cheap starters (and Bennett took a 1-year $5M "prove it" deal. I'd say he proved it.). Of our starting 22 at the beginning of the year, 9 had a base salary of less than $1M. Hooray rookie deals!
* This does mean our piper will have to be paid soon. Notable FAs this year: Michael Bennett, Golden Tate, Brandon Browner, Walter Thurmond, Doug Baldwin (RFA). Next year: Chris Clemons, Cliff Avril, Earl Thomas, KJ Wright, Richard Sherman, Byron Maxwell, Malcolm Smith, Jermaine Kearse (RFA).
* Our FO already knows we can't keep everyone together forever, and they aren't afraid to make moves. If they think they can replace a good player with one that's cheaper, they will. Since Carroll took over in January 2010, the Seahawks have made 1105 transactions. (The Patriots have the second most with 964.) They're unafraid to churn the roster and fail; Carroll's first "big" acquisition? Charlie Whitehurst. Yeah.
A lot of us think that Sidney Rice ($7.3M cap savings according to Overthecap.com) and Chris Clemons ($7.5M) will get cut, and Red Bryant ($5.5M) is on the bubble. FA Brandon Browner (starting RCB) isn't likely to get re-signed, and we're not sure about Thurmond.
I think I rambled more than I intended to, so if you have any other questions I'll do my best to answer them. Maybe I can rope in one or two of the Field Gulls regulars if need be!