It's not just the offense

So maybe a 1-3 record after four games isn't the end of the world, especially when you consider that the Vikings are only one game behind 2-2 Green Bay and Chicago for the division lead in the NFC North. In general, people are pointing to two reasons for the Vikings' slow start: a lackluster offense (accompanied by some of the worst play calling in the league) and the rough opening schedule: road games at Green Bay and undefeated Tennessee and home against Peyton Manning and the Indianapolis Colts. Next week, the team plays at New Orleans, where Drew Brees figures to throw for at least 350 yards.

But here's another theory: Apart from a dismantling of the Carolina Panthers, the defense, pumped up by high-priced free-agent acquisitions, has looked mediocre at best, forcing very few turnovers, rarely hassling the opposing quarterback and, in general, looking just like the defense of the past few years: solid against the run, porous against the pass, and unable to make a stop or make the big play when it needs to. So, just how has the defense looked the first four games?

Here are some of the key defensive stats from Minnesota's first four games:

	Yards	Sacks	Turnovers	Points
Green Bay	317	0	0	24
Indianapolis	321	2	2	18
Carolina	204	5	2	10
Tennessee	275	0	1	30
Average	279.25	1.75	1.25	20.5

Now, here are the offensive stats for those four teams over the 11 games they've played (three for each except Indianapolis) against non-Vikings teams and their per-game averages:

	Yards	Sacks	Turnovers	Points
Green Bay	962	9	2	85
Indianapolis	618	3	3	34
Carolina	1005	4	2	70
Tennessee	947	2	4	72
Average	321.09	1.64	1.00	23.73

Looking at that, you'd say, for the most part, that the Vikings defense has performed well, doing better than average in yards, turnovers, and points allowed, while only being a smidge off the sack rate.

However, as you can see from the first table, much of the Vikings' statistical defensive success comes from a thrashing of Carolina in week 3, when they established or tied their highs in yards allowed, sacks, turnovers, and fewest points allowed. Let's take out Carolina's stats -- the team's only win -- from each chart. I'll abbreviate the charts by just presenting the Vikings' average defensive stats and the average per-game stats of their three opponents in the eight other games they've played:

	Yards	Sacks	Turnovers	Points
Minnesota actual (Avg vs. non-Car)	304.33	0.67	1.00	24.00
GB/Ind/Tenn (Avg vs. non-Min)	315.88	1.75	1.13	23.88

So, what can we say about this comparison? The first thing is that it is a small sample size -- only, in effect, 11 games total, so any analysis has to come with a grain of salt.

That said, it's clear that the Vikings defense has, at best, performed at an average level against the three teams it lost to so far this year, at least from this limited data. Yards, turnovers, and points are nearly equal, and the sack totals are way off. The Vikings managed just two sacks in three games against Green Bay, Indianapolis, and Tennessee, while other defenses have sacked those teams' QBs 14 times in eight games. And this is with the Vikings boasting what's supposed to be the best defensive front (if not front seven) in the league.

It's too early to give up on the season (and we do still have two games against Detroit, always a plus), but it's also a bit of a fallacy to blame the Vikings' early struggles entirely on the offense or on a tough schedule. Other teams have played the same teams we've played and, in general, done the same or better defensively than the Vikings. The Vikings' defense wasn't supposed to be league-average, and its pass rush certainly wasn't supposed to be below average. But that's what they are right now, and it's a big reason the team is 1-3.