The NFC North's new Air and Space passing dynamic was one of our central themes last season, and so it follows that pass defense will emerge as a critical variable in 2010. That's why I suggested we track a significant sliver of the Chicago Bears' efforts to improve against the pass, and I think we should do the same thing for the Detroit Lions.

The Lions, after all, finished the season with the NFL's worst pass defense from just about every angle imaginable. And as we discussed in March, their performance against Minnesota and Green Bay was worse than their season averages. Offseason excitement generated by new offensive skill players and an overhauled defensive line will mean nothing if the Lions can't slow down opposing passing games.

First, let's establish the brutal ground floor. As the chart on the right illustrates, the Lions allowed more yards and touchdown passes than any NFL team last season despite having the 12th-most attempts against them. That means opponents were especially efficient, completing 68.1 percent of those passes and averaging more than eight yards per attempt.

Those numbers were worse against the Packers and Vikings, who completed 74 percent of their passes against the Lions for nearly a full yard more per attempt. As much as anything else I've ever typed, I feel confident those numbers speak for themselves. No need to rub it in.

So where should the Lions focus their efforts? Even before we asked this question, the Lions prioritized their pass rush by acquiring three new starters for the defensive line. They're hoping that defensive end Kyle Vanden Bosch, along with tackles Ndamukong Suh and Corey Williams, can elevate play-by-play pressure well beyond last year's total of 26 sacks.

If they can, they'll likely make a dent in some hard-to-fathom microfigures conjured this winter by ESPN's Stats & Information. Whereas we pinpointed the Bears' short-range defense last week, a trend many of you attributed to the pre-snap positioning of their cornerbacks, here I think we can safely start with the Lions' downfield defense when suggesting a root of their problems.

As you can see in the next two charts, the Lions were one of the NFL's worst teams last season in defending passes that traveled at least 21 yards in the air. Opponents completed more than half of those throws, averaging more than 41 yards per completion.

You could fairly note that these plays accounted for less than 10 percent of the total attempts. But those plays led to a disproportionate amount of production. In other words, opponents threw 23 percent of their touchdown passes and amassed 24 percent of their total yardage on 8.9 percent of their passing plays. The tangential opportunities created by such success only compounded the Lions' deficiency. So if you're looking for an initial way to bring down opponents' passing totals, that's as good of a place to start as any.

It stands to reason that a more consistent pass rush will limit the time for long pass plays to develop. But will that be enough? Don't forget the Lions have also turned over five of the seven base positions who regularly figure in coverage. None of the expected replacements have, shall we say, the name recognition now associated with the defensive line. In fact, as organized team activities continue, the only clear starter in the secondary is safety Louis Delmas.

Can an improved pass rush alone stem the near-unfettered view opposing quarterbacks had of deep routes? The Lions might not have much choice. To illustrate that view, consider what coach Jim Schwartz said after the draft about the derivative ways that Suh will help the Lions in addition to his role at the point of attack:

"He'll help our corners out because we won't have to blitz as much," Schwartz said. "He'll help our run defense out, and help our corners out again, because with him up there, he's hard to come off double-teams and we may not have to spin our safety into the box as much."

As I did last week, I'd like to throw this topic out to the cyberfloor before finalizing the way we'll track the Lions' pass defense this season. Other than explosive passes, what other defensive benchmarks do you envision? Turnovers? Their 23 takeaways last season ranked No. 25 in the NFL. Run defense? Although less germane in the new NFC North, the Lions ranked No. 25 last season by giving up 126.6 yards per game.

Let me know in the comments section below. I'll review your submissions and come up with a regular blog staple by the time the regular season starts.