At some level it might seem hard to take Detroit's defense seriously, because for the past two seasons this unit has been nearly legendarily bad.

For proof, just consider this. In 2009, Drew Brees led the NFL in passer rating with a 109.6 mark. The Lions' defense gave up a 107.0 rating for the season. That means every quarterback was about as good on average as the most efficient quarterback in the league when facing Detroit's passing D.

After breaking down game tape and crunching some numbers, I can say without a shadow of a doubt that this year's Lions defense is nothing like its 2009 cousin.

A good place to start is passer rating. Detroit so far has allowed a passer rating of 83.4 to opposing quarterbacks. That isn't an elite number by any stretch (it currently ranks 21st in the league) but it is a huge improvement over last year.

The Honolulu Blue and Silver are also doing a great job of forcing bad decisions. Bad decisions are a tape-based metric that gauges how often a quarterback makes a mistake that leads either to a turnover or a near turnover (e.g. dropped interception, fumble recovered by the offense, etc.). It is a somewhat subjective statistic, to be sure, but over the years it has proven to be a very good barometer for measuring passer error levels.

A quality mark in this metric is anything over 3 percent, and the Lions are currently forcing bad decisions at a 5.7 percent clip. It is a key reason why they have seven interceptions, a total that ties them for fifth-most in the league in that category.

Last but not least, Detroit defensive coordinator Gunther Cunningham has done a fine job of getting better play out of his cornerbacks. In the past couple seasons, Detroit seemed to have a revolving door of corners who would give up at least nine yards per attempt (which is the bar that indicates someone is probably a coverage liability). This year, that has changed dramatically, as both Chris Houston and Alphonso Smith -- the Lions' starting cornerbacks -- have YPA totals of under six yards.

What all of this means is, the Giants cannot take this defense lightly. If they do, it could be costly, as Detroit is more than capable of pulling off an upset.