How big of a concern is Patriots' D?

The 14-1 Green Bay Packers have allowed the second-most yards in the NFL. The only team to allow more yards is the 12-3 New England Patriots.

Clearly, yards don't mean as much as some would have you believe.

But can anything be learned from the seeming disparity between defense and wins?

This will be the first time in the Super Bowl era that a team finished last in yards allowed and made the playoffs.

Of course, the Patriots aren't just last in the NFL. They are on track to allow a historic number of yards. With one game still to play, the Patriots already have allowed more yards (6,175) than any team to make the postseason. The previous high belonged to the 1981 Chargers (6,136).

In the past 60 seasons, only the 1981 Colts allowed more yards per game than the Patriots have this season. That team finished 2-14 while setting the record with 6,793 yards allowed.

The Patriots would have to allow more than 600 yards in Week 17 to exceed that. Far more likely, the Patriots will become the second team in NFL history to allow 6,500 yards in a season. The 2008 Lions fell 30 yards shy of that during an 0-16 season.

If the Patriots allow just 135 pass yards on Sunday, they will surpass the 1995 Falcons for the most allowed in a single season.

Of the previous 37 teams to allow more than 6,000 total yards in a season, only four made the postseason. Already in 2011, we can add two teams to that list in the Patriots and Packers. Both the Saints and Giants could join them.

There's clearly a flaw in measuring defense by yards allowed. But that doesn't totally explain how the Patriots have pulled this off.

Not to be lost in the discussion is offense. The Packers, Saints and Patriots are the top three teams in point differential. New England is on track to become just the sixth offense in NFL history to gain 6,700 yards. The Packers have the fifth highest scoring average in league history.

Entering this season, the Patriots were 6-32 all-time when allowing 450 or more yards. This season, they are 5-0. But with such a high-powered offense, it's not hard to understand their success.

The top three scoring defenses (49ers, Steelers, Ravens) all rank in the top four in yards allowed. So how is it that the Patriots rank 32nd in yards allowed but 14th in points allowed?

Part of it has to do with turnovers. The Patriots' plus-14 turnover differential ranks third in the NFL, and the team is tied for fourth in the NFL with 30 takeaways.

The Patriots also have displayed a bend-but-don't-break defense. Consider that they've allowed 86 plays of 20 or more yards. That's 10 more than any other team and the most for any team in the past 15 seasons. Yet, of those 86 plays, only five went for touchdowns.

Last season, the Broncos allowed 84 plays of 20 or more yards. Twenty of those plays were touchdowns.

The 2011 Steelers have allowed only 39 plays of 20 or more yards, which is less than half of New England's total. Yet somehow, the Patriots and Steelers have allowed the same number of touchdowns of 20 or more yards.

The Patriots also held held their own in the red zone. While they've allowed their opponents 58 trips inside the 20 (third most in the NFL), only 81 percent of them have ended in scores of some sort. That's the sixth-lowest rate in the NFL.

New England has six takeaways in the red zone, tied for second in the league behind the Falcons (seven).

In terms of red zone touchdown-to-field goal ratio, the Patriots' defense is around the middle of the pack (as compared to back of the pack in most other categories): 53.4 percent of opponent red zone trips ended in touchdowns, 18th best in NFL (average is 52.3 percent).

The Patriots allow 6.20 yards per play overall (31st in NFL), but in the red zone, that average drops to
2.61 yards per play (13th in the NFL).

That seems to be the story of the 2011 Patriots defense. Let them have their yards, but keep opponents off the scoreboard.

Jeremy Lundblad is a senior researcher with ESPN Stats & Information. He provides statistical analysis for ESPNBoston.com.