The Minnesota Vikings head into Week 4 as the only NFL team without its starting quarterback and starting running back from Week 1. Pro Football Focus says their tackles have been terrible. Armchair quarterbacks wonder why Cordarrelle Patterson isn't seeing more touches. They rank 29th in total offense and 28th in scoring offense. On the other hand, the new-look Vikings defense is keeping them in games and, through three weeks at least, appears to be much better.

The normal caveats apply here. Yes, it's only been three games so the sample size isn't ideal. No, the defensive doesn't have a very high hurdle to clear to appear to be improved over recent seasons in which they were among the worst in the NFL.

Having said that, you can't help but be impressed by the defensive enhancements we're seeing under head coach Mike Zimmer. His defensive acumen is a big reason he was hired to lead the Vikings, and so far the changes are noticeable both in terms of the eye test and statistically.

The defense absolutely destroyed the Rams in Week 1.

The defense couldn't really be held accountable for 17 of the Patriots' 30 points in Week 2: New England had a one-yard touchdown "drive" off an interception, a field goal following a 17-yard "drive" that started with possession at the Vikings' 45-yard line because of an interception… and, of course, a blocked field goal that was returned for a touchdown.

Then in Week 3, aside from a game-plan hiccup by the defense that Zimmer himself took the blame for, the Vikings defense kept them in their game with the Saints. Zimmer noted afterwards that he was planning to trick the Saints, but they ended up changing "a lot of things in what they did with some of their reads." The mighty New Orleans' offense was held to three points over the final three quarters. Drew Brees didn't throw for 300 yards or three touchdowns. Jimmy Graham was held out of the end zone and didn't have a chance to dunk the ball over the goal post. Those things don't happen too often.

Now, this is not to say the Vikings' defense has been perfect or lights out or anything like that. The obvious aggression on defense has yet to lead to many turnovers – just two interceptions, zero fumble recoveries. Xavier Rhodes' pass interference penalties were an issue in Week 2. Captain Munnerlyn's roughing the passer penalty (despite what you think of the call) was a pivotal play in Week 3. They rank 21st in third-down defense, allowing a 43.9 percent conversion rate. Needless to say, turnovers, penalties and third downs are significant.

Without question there are things to clean up, and the injuries to defensive captain Chad Greenway won't make the cleanup any easier.

But here are some positives to consider:

The Vikings rank 11th in total defense, 13th in pass defense and 15th in rush defense. They rank ninth in scoring defense (18.7 points per game) even including the 17 points that were gift-wrapped for the Patriots. I'm sure all teams have handed the opposition points off turnovers and miscues this season, so ranking in the top 10 is impressive for a Vikings team no matter how you slice it.

And for all the bashing certain Vikings players have received at the hands of ProFootballFocus.com, let's give some equal time to the guys getting good grades on defense.

Of the 73 defensive tackles graded by PFF, Tom Johnson is at 18 and Sharrif Floyd is 25.

Of the 29 outside linebackers in 4-3 sets graded by PFF, rookie Anthony Barr is tied for No. 6.

Yeah, Rhodes and Munnerlyn have taken a beating in the grading system, but Josh Robinson is the No. 9 cornerback through three games per PFF. That time he spent in Zimmer's doghouse might have done him some good.

Of the 76 safeties graded by PFF, Robert Blanton is at 27.

Oh, and Harrison Smith is No. 3 at safety – right behind Pro Bowlers Eric Weddle and Earl Thomas. Then again, I don't think anyone who has watched a Vikings game this season needed the fancy PFF metrics to tell them Smith has been outstanding. Watch the games back on NFL rewind or catch a replay on NFL Network if they have one this week. He's all over the place. He's been the Vikings' best player so far this season.

The Vikings welcome the Atlanta Falcons to TCF Bank Stadium this Sunday. The Falcons own the NFL's No. 1 offense in terms of both yards and points through three weeks – though the Vikings' last head coach and current Buccaneers defensive coordinator, Leslie Frazier, is partially responsible for their inflated stats, as anyone who watched the lopsided Thursday night game between the Falcons and Buccaneers can attest.

We'll find out just how much this new-look Vikings defense has improved this Sunday against Matt Ryan, Julio Jones and the potent Dirty Birds.

Head on over to VikingsJournal.com for a look at some veteran running back options for the Vikings and some positive signs for the Teddy Bridgewater Era.

Bo Mitchell is the Vice President of Content at SportsData, head writer at VikingsJournal.com, co-host of the Fantasy Football Pants Party at 1500ESPN.com and a member of the Pro Football Writers of America.

You can follow Bo on Twitter at @Bo_Mitchell