As a longtime lurker and very rare commenter, this is my first fanpost. Reading through the SBN projection for why the jets would make the playoffs, the Jets defense was mentioned as the 20th best defense in the league last year. This struck me as outrageous enough to warrant a response, and as my comment grew too long a fanpost seemed like a more appropriate medium. I'm a big believer in the DVOA system created by the good people at http://footballoutsiders.com/ (explained here for those unfamiliar), and thus the basis for this fanpost is the metrics available at their website.
In 2011 the Jets were ranked 2nd in total defense among all teams by DVOA, second only to the Ravens. We were 2nd against the pass and 4th against the run (stats available here). While In 2010 the Jets were ranked 5th by FO metrics (http://footballoutsiders.com/stats/teamdef2010), 7th against the pass and 2nd against the run. This is a far cry from the commonly raised opinion that the Jets defense has steadily declined since they lead the league in '09.
It seems counter-intuitive for the 2011 D to be considered better than the '10 one, but there are a few factors that played into this:
Offense- In 2010 the Jets offense was ranked 16th overall by DVOA and 5th in rushing. A year later the Jets dropped to 21st overall and 18th in rushing. Without the ability to run the ball as well, our command over time of possession dropped by almost two minutes per game on average and our defense routinely seemed gassed near the end of games. The end of the Denver game still haunts my dreams.
Turnovers- From 2010 to 2011 the turnover ratio decreased from a solid +9 to -3. With the defense regularly dealing with opposing teams starting in field goal range due to crushing turnovers, points were given up more frequently that the D had little chance to stop.
Variance- Both the 2010 and 2011 Jets were marked by inconsistency on the defensive side of the ball. This is measured in DVOA where the Jets ranked 28th in 2011 and a staggering 31st in '10. The rankings indicating how consistently the unit performed on a weekly basis.
Looking at all of this, I can easily imagine the 2012 Jets defense being even better than last year with the aid of a hopefully improved offense under the supervision of Tony Sparano. Turnovers killed us last year and our inability to run the ball effectively didn't help. However, we retained the best set of corners in football and have the addition of Coples/Davis and the progression of Wilkerson/Ellis in the front 7.
The premise for this is obviously the acceptance of the FO metrics, but I can't imagine a world where Rex Ryan allows his defense to become a weakness anyway.