By pretty much any measure, the Jets had a really good defense last year. They gave up the fifth fewest yards in the league. That is impressive in any context, but it is unbelievable when you consider they played seven games against opponents with top ten offenses and eleven games against offenses ranked in the top half of the league. The defense was one of the best even though it played against one of the least favorable schedules in the league.
The unit might not have been as dominant as it was in 2009, and there were glaring holes at safety and linebacker. On the whole, the Jets were able to overcome these issues. You might say that the team gave up too many points, but that is because the offense gave the ball away a ton. The Jets actually allowed 7.8 points per game off turnovers. Think about that! The offense was spotting the other team more than a touchdown a game. The defense itself allowed 14.8 points a game, a very good number.
The offense was clearly the issue with the Jets a year ago. They were better equipped to get around their problems on defense. The holes at safety and linebacker are more important to fill for the Jets than they would be for most teams in the same spot, though. It has to do with the competition.
The New England Patriots are built to eat teams alive that cannot get to the quarterback without blitzing and have suspect safety play. They have a quarterback as good as anybody in the league at diagnosing and carving up blitzes and a pair of athletic tight ends who torture slow safeties. AS things exist right now, this offense is built well to take on the Jets. This is no accident either. The Pats and Jets have been playing an elaborate game of chess for years in the way they have constructed their rosters. The Jets drafted Nick Mangold because the Pats had Vince Wilfork. The latest incarnation of this came with the Randy Moss trade. Many observers felt Tom Brady force fed the ball to Moss too frequently and ignored his other weapons. This could spell doom against a team that had corners who could take Moss away like the Jets. The Moss trade moved New England to a more balanced offense built on tight ends, much more favorable against the Pats' main competition. This is not to say it was the only reason New England traded Moss. There were many factors, including a diminishing skillset and contract uncertainty, but the way it impacted the head to head matchup with the Jets likely played a role.
Considering how the Pats have looked the last few years, they seem like a virtual lock for 12 wins as long as everybody stays healthy. The Jets pretty much need to sweep New England to have any chance at winning the AFC East. The rest of the league will not be much help. In the Rex Ryan era, the Pats have a .571 winning percentage against the Jets in the regular season and Playoffs and a .760 winning percentage against the rest of the league.
There might be isolated games where a blitz heavy look gets to Brady, but he will eventually figure out a defense, lock in on a favorable matchup, and do damage. His safeties will eat slow safeties like Eric Smith alive. The Jets need to beat the Pats to win the division. They need to win the division to avoid an exceptionally difficult path to the Super Bowl. Ergo better safeties and pass rushing outside linebackers are necessary.