All that stood between the Seattle Seahawks sealing back-to-back Superbowl wins was one yard and an undrafted cornerback out of West Alabama. We all know what happened, of course. But to think about how rare that feat has become, with New England being the only team to repeat since John Elway's Broncos did you-know-what in '98, it's almost unfitting that Seattle blew it with a matter of inches to claim.

And it's unfitting because, in a league where the rules are so clearly skewed to favor offense, Quinn and the Seahawks won with defense. This past season, the unit ranked No. 1 in total defense (267.1 YPG), No. 1 in passing defense (185.6 YPG) and No. 3 in rushing defense (81.5 YPG). The unit was also the league's least penalized, drawing 21 fewer flags than the next-best Jets and Falcons, and held opponents to a 37 percent success rate on third down. (The Falcons, you'll remember, were dead last in that category.)

They didn't make an ungodly number of interceptions. They didn't lead the league in sacks. The Seahawks simply played clean, fundamental defense and excelled at beating you with their no-frills scheme.

There was a bit of contention last offseason as to how exactly the Falcons classified their scheme under Mike Nolan. With the signings of Tyson Jackson and Paul Soliai, all signs pointed to more 3-4 looks. But the Falcons were still ill-suited to line up that way from the standpoint of their linebackers, and that clearly showed as the team continued to rely on the nickel package. So you could have called it a "base nickel" defense (I still like calling it the Shitz Blitz defense). Regardless, nobody was calling it "good."

Quinn (and his defensive mentor Pete Carroll) primarily employed a "4-3 under" defense. There's a handful of 4-3 variations in the NFL (over, under, even, flex, bear), and they all refer to how the front seven is aligned. But first, a little crash course in gaps and techs for those looking to learn.

There are three primary gaps a defender will know: 'A,' 'B' and 'C.' The A gaps are between your center and guards, B gaps between the guards and tackles and C gaps either between the tight end and tackle or simply the outside if there is no tight end. (Please excuse the shoddy illustration).

So you can see the gaps noted there. The numbers are techniques or "techs," and they are used by coaches to denote exactly where the defensive linemen will line up. So for instance when scouts or wannabe scouts use lingo like "he projects as a three-technique lineman at the next level," this is what they're talking about.

Back to Quinn and the 4-3 under. Usually, this involves a defensive end occupying the 4-tech or the 7-tech on the strong side, a bigger-bodied tackle at the 1-tech on the strong side, a 3-tech defensive tackle on the weakside and then a weakside defensive end lined up on the edge/outside of the line. That last weakside end is also known as the LEO linebacker and is a player who has the versatility to rush from a three-point stance (hand in the dirt) and rush standing up. He is more or less a designated pass rusher.

Behind them are the three linebackers: WILL (weakside), MIKE (middle) and SAM (strongside). Now here's where things get a little funky. In "under" alignment, the line is essentially weighted to the weakside. To compensate for that, Quinn could shift his linebackers to the strongside if he wanted to play aggressive (see this great breakdown from Ben Muth).

As you can see above, which is taken from Muth's post, the WILL is playing the A-gap and the MIKE is playing the B-gap. The SAM is lined up well to the outside. It looks a lot like a 3-4, doesn't it? That's the flexibility the LEO offers, and it gives a coach the ability to keep a consistent pass-rushing threat on the field at all times.

We know LEO equals pass rusher. The 3-tech DT, sometimes called the "under" tackle, will be a little quicker and a better penetrating pass rusher type (think Jonathan Babineaux or Rod Coleman). The 1-tech DT will eat up a double-team (a la Paul Soliai), and the strongside DE will be a stronger, more run-oriented defender that will also have to handle double-teams -- he basically functions as a 3-4 lineman.

The SAM linebacker is also an incredibly important position in this defense because he will be called upon to handle a number of different duties. Obviously, being on the strong side means he needs to be able to shed blocks and play stout run defense. However, he also has to possess cover skills, as he'll sometimes drop in a zone or be matched up with the tight end (remember Gronkowski burning whatever linebacker was covering him in the Superbowl?). Opposite him, the WILL is usually smaller and quicker -- an attacker that will occasionally provide blitz pressure. And the MIKE of course handles pre-snap adjustments and functions as a jack of all trades.

How might the Falcons look in this alignment? I think it's safe to say there will be plenty of personnel changes this offseason, but an early guess might look like this:

LEO: Jonathan Massaquoi

3T: Ra'Shede Hageman / Jonathan Babineaux

1T: Paul Soliai / Corey Peters

SDE: Tyson Jackson

WILL: Prince Shembo / Joplo Bartu

MIKE: Paul Worrilow

SAM: Sean Weatherspoon

The obvious problem here is that Worrilow (still) does not possess the cover skills for an inside linebacker, so like many I expect the Falcons to address that position this offseason. Massaquoi is the only guy on the roster I see as having the quickness to play LEO, which as I said basically functions as a designated edge rusher.

Now for pass coverage in the secondary, which as others have noted employs lots of Cover 3. As a reminder, that's where the deep half of the field is covered by three players -- two corners and a safety (usually the free safety). The strong safety will often line up closer to the action, as Kam Chancellor did in Seattle, to serve as an "in the box" defender that can play the run or drift into a shallow zone.

For the Falcons, Desmond Trufant and William Moore should do just fine, and I'd love to see what Kemal Ishmael can accomplish with another offseason under his belt. No real worries here.

One last topic I'd like to cover is how these defenses were built. Richard Sherman was a 5th-round draft pick. K.J. Wright was a 4th-round draft pick. Byron Maxwell was a 6th-rounder and Brandon Browner went undrafted. The only area of that defense that wasn't built through the draft was the defensive line, which was the product of a relatively affordable string of free agent signings (Cliff Avril, Michael Bennett, Tony McDaniel, Kevin Williams).

The Falcons' front office has already shown that it can scout well in the secondary (Trufant, Moore, Ishmael, Brent Grimes). Where this team so clearly suffered under Smitty and Nolan was its front seven, where a mess at linebacker coupled with a scheme that generated no pass rush led to a lot of bad defense. And of the only two "big-name" pass rush signings, one was disappointing (Osi Umenyiora) and the other was an unmitigated disaster (Ray Edwards).

I think the hiring of Richard Smith, who did an excellent job of developing Danny Trevathan and Brandon Marshall in Denver, will help plenty in regards to talent acquisition at linebacker. As for the line, hopefully this coaching staff will be less inclined to spend all its money on run-stoppers.

If those two areas improve quickly, this defense may not be too far away from a revival after all.