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Everyone knows the Minnesota Vikings have struggled against the pass this year. However, few realize just how historically bad they are on pace to be.

Currently, according to Pro-Football-Reference.com, the total rating for quarterbacks going against the Vikings (defensive QB rating, or DQBR) is a staggering 107.1. If they keep up this pace, that would put the 2011 Vikings pass defense as the third worst in history, behind only the 2008 Detroit Lions (110.9) and the 2011 Indianapolis Colts (108.7 through 13 games).

Opponents are completing 68.7 percent of their passes and have a 4.25:1 touchdown-to-interception ratio against the Vikings.

Some people would argue that since this is a passing league, the DQBR for the entire league would be higher this year than in the past, and therefore the high number for the Vikings (and Colts) is not that out of line with the rest of the league.

Well, running a basic statistical analysis on this year's numbers, we find the Vikings DQBR is 2.30 standard deviations away from the mean (NFL average DQBR: 84.27). This would be fifth-largest deviation in the last 20 years.

There are many reasons for this: injuries, off-the-field legal issues and a new coach in charge.

Injuries have decimated the Vikings secondary, with All-Pro cornerback Antoine Winfield and safeties Husain Abdullah and Tyrell Johnson all being on the injured reserve. The other opening day starting cornerback, Chris Cook, has missed most of the season due to off the field legal issues. In addition, cornerback Asher Allen and safety Jamarca Sanford have been nicked up at various points in the season.

The only defensive back to not appear on the injury report this season has been cornerback Cedric Griffin, who is recovering from the ACL tear he received in the 2009 NFC Championship Game against the New Orleans Saints.

The secondary isn't the only thing to blame. The Vikings linebacker corps has not been doing the secondary any favors. MLB E.J. Henderson has looked slow all season after recovering from injuries suffered the last few seasons. His brother, Erin, has certainly improved over the course of the season, but still has a long way to go.

This is not to say there hasn't been a bright spot on the defense. The Vikings are third in the NFL in sacks with 40, including 17.5 by Jared Allen and six by Brian Robison. Normally, you'd expect this amount of pressure to lead to an increased number of turnovers, but it has not as the Vikings only have six interceptions on the season, and none since Week 5 against the Arizona Cardinals.

This week, the aforementioned Saints (10-3) come into Minnesota with a devastating passing attack and a chance to keep the pressure on the San Francisco 49ers (10-3) for the second seed in this year's playoffs.

Look for the Vikings DQBR to continue to rise as they will be starting rookie Mistral Raymond at free safety and likely having Benny Sapp, who was released by the Miami Dolphins earlier this season, as cornerback opposite Asher Allen. Griffin has started the last few weeks, but coach Leslie Frazier didn't seem to happy with his play last week against the Detroit Lions, benching Griffin in favor of Sapp in the second half.