The Seahawks defense just held the Browns offense to six points while on the field for nearly 43 minutes. I could point out Colt McCoy is not a very good quarterback, the Browns were without their number one running back, and they lost Mohammed Massaquoi and Benjamin Watson during the game, leaving Greg Little as the only reliable receiver on the field. Those are certainly facts worth pointing out, as you'd figure most other offenses would have been able to do more with the allotted time, but this performance was still good.
Pundits like to just split defense into "good" or "bad", but that's a poor representation of NFL reality, even if you detail it down to run and pass defense is. The fact is many defenses in the NFL are built specifically to enable the team to beat its divisional rivals, or in some cases built to match their own offense's scoring or ToP capacity. The most obvious example of this is the Colts defense. The Colts are collapsing not just because their offense is much worse, but because their defense is built to play against offenses playing catchup. That, and a dearth of talent due to a streak of bad drafting, is what made the loss of Manning have such a major impact.
I have never been completely dismissive of Seattle's unusual, rather gimmicky defense, but I do not think this defense is inching towards "elite" or capable of winning us many games if the offense keeps being up and down. Right now, by the traditional ( and usually useless) "total yards" stats, the Seahawks defense is 15th overall, 11th against the run and 20th against the pass. Only the Colts see more run attempts per game (35.1) than us (33.5, tied with the Rams), but we're leading the league with 3.1 YPC. For a more detailed look: Our best run defense is up the middle, 2.67 YPC (2nd in the NFL), and teams avoid running up the gut against us (24th in the NFL). Opposing teams tend to run to offensive right guard (2nd in the NFL) and right tackle (5th) more than offensive left guard (7th) and left tackle (8th). We rank 10-11th for each of these spots allowing about 3.5 YPC except offensive left guard, where we rank 7th allowing 2.75 YPC.
In advanced stats, Football Outsiders has us as 12th in the league, mostly due to an excellent run defense, 4th in the NFL, while our pass defense isn't very good, 21st in the NFL.
Like I said, defenses tend to be constructed keeping the divisional rivals in mind and that seems to be the case for us. Our corners specialize in larger but not overly fast wide receivers like Larry Fitzgerald or Michael Crabtree. The Rams and 49ers are both teams with limited quarterbacks that need to establish the run game to be able to win games.
But our defense doesn't seem good enough to transcend matchup strengths, like the best of the NFL do, and that's where we fall far short of "elite". Ben Roethlisberger and Eli Manning absolutely ate us up for about ten yards per attempt, and I shudder to think what the truly elite quarterbacks would do to this defense. Single out the offenses we play well against, and the pattern is obvious, they're all teams that need to establish the run and are loath to depend too much on their quarterbacks, either because they're young or just not very good. The 49ers and Browns are the most obvious examples, but it applies to the Cardinals too (mostly because Kolb just isn't very good so far, and is very fond of checking down), as well as the Falcons, who have a good quarterback but definitely prefer to establish the run and take what's given in the passing game.
Teams we have left that are built with a high number of rushing attempts or output and little from their quarterback are the Bengals, Rams (twice, unless Brandon Lloyd and easier matchups turn that team around, which is possible), 49ers and Cardinals. Teams that, going by current trend and defensive build, should be able to absolutely shred us are Dallas, Baltimore, Philadelphia and Chicago, with no idea what I should think of the Washington offense. This is prognosticating, which I'm not very good at, so just figure for things to go exactly the opposite way.
The scheme is pretty obvious. Teams that depend on steady chunks from their run game to get to the first down marker find themselves coming short against the Seahawks. Our corners are specialized in outfighting receivers for the first few yards, denying easy outs, while the linebackers and Kam Chancellor cover the tight ends and the flats. Between the lot of them, most of the quick and short passing options are either gone or too ineffective to get enough yards. But many better offenses will just sit and wait for longer options to come free, which the defense needs to counter with pass rush.
Any and every Seahawks writer or fan has been pointing it out, the Seahawks have a need for more pass pressure (from the 3-tech, mostly) and higher-end corners. Our pass rush actually seems to be improving as we figure out our defensive rotation, but our secondary is a huge problem. Our safeties have been fairly impressive, though safety play is really hard to judge without All-22. A lot of attention is going to Kam Chancellor because he spends more time near the line and thus is making plays we get to see. My impression is Earl Thomas still gets the tougher assignments and is the better player overall, but I don't want to commit to too much of a judgement other than "they've both been good".
But safeties can only make up so much for corner play, and that's where the problem was even before we lost our two best corners. Now we have the 6'4 Brandon Browner and 6'3 Richard Sherman at corner, two guys most teams would've converted to safety. While both have impressed me with their fluidity of motion for their size, this is definitely not the corner duo I would've hoped to see start the rest of the year for us.
In a weekend of terrible football, the Jaguars upset the Ravens by holding them to 7 points. Does that create hope for us to upset them? I wouldn't say so, because if you watched that game it was impossible to ignore how important tight man coverage all over the field was to limit the offense. Jacksonville is a very good defense (6th in DVOA, 5th against the run, 8th against the pass) and managed to both limit Ray Rice and then take out the wide receivers. That's the difference between their and our defense. We can limit Ray Rice, but we can't take away the wide receivers. Our defense is predicated on challenging the quarterback to beat us, and that works against the various bad quarterbacks and limited passing games we've faced, but many quarterbacks faced with such a challenge will take it, and gobble it up.