The Vikings once again have the best third-down defense in the NFL.

In 2017, the Vikings set an NFL record for the best third-down stop rate in history, allowing a conversion on just 25.2% of third downs.

In 2018, at least through the first six games, the Vikings are somehow even better, with a 25.0% conversion rate.

In a world of rising points totals, explosive passing offenses, and pro-QB rule changes Mike Zimmer stands as a bulwark that defense still matters. Zimmer’s third down defense held the Cardinals to 0/10 on third down (and 0/2 on fourth down) last week through brilliant blitz scheming, pre-snap disguises and complex coverage concepts that made Josh Rosen’s day a living nightmare. Here are each of those failed third down conversions, and what made them work:

Mack’s Sack

Mackensie Alexander got a sack on the overload blitz detailed below:

The Vikings come out in a 3-3-5 alignment (meaning three defensive linemen, three linebackers and five defensive backs), and pre-snap, the Vikings initially overload the left side of the line. Josh Rosen and the center adjust their pass blocking plan accordingly by sliding the protection left—basically the offensive linemen will block the gap to their left (except the right tackle, who blocks Hunter because of he’s lined up so wide).

Once that protection gets set and Rosen drops back for the snap, all three linebackers showing blitz drop back into coverage, and instead the two slot corners (Mackensie Alexander and Anthony Harris) blitz. The right B-gap (between the right tackle and guard) is wide open, because the right guard follows Linval Joseph as he stunts inside, and the right tackle has to deal with Danielle Hunter’s speed rush from his wide alignment. Those two rushes part the gap like the red sea, and Rosen just has no chance.

By the way, the Vikings ran a very similar disguised overload pressure in week 1 against the 49ers. That play call resulted in Mike Hughes’ pick six:

Shot 2 – It's not just the A gap pressure schemes with Zimmer at this point though, because they work in a lot of good overload zone blitzes as well. Show the defense one thing pre-snap and present something different after. Effective for the #Vikings so far #FlyEaglesFly pic.twitter.com/KfZlLcq01s — Fran Duffy (@fduffy3) October 4, 2018

Smith’s Sack

Zimmer’s favorite third down pressure package is the “double A-gap” look that gets both linebackers on the line showing blitz, often with Harrison Smith showing blitz on the edge. That was the pre-snap look Josh Rosen got on this next play:

What makes this look so deadly, and what’s caused other teams to copy it straight out of Zimmer’s playbook, is that it’s just hell to predict who’s dropping into coverage and who’s blitzing. Zimmer might bring all seven, in which case the QB needs to bring in extra protection and make a quick hot read (and hope he gets it right!), or he might rush only three and drop 8 in coverage.

Here, Rosen slides protection left (technically a half-slide, where the C, LG and LT block the gap to their left, and the RG & RT block their man to the right, and the RB blocks anyone else, looking especially for any LB blitz from the inside). The Cardinals are trying to run a slot screen here, where Larry Fitzgerald (aligned in the slot in the bunch formation on the right) runs out to the flat, as the other two WRs in the bunch right straight for the defensive backs upfield to block for the screen. Rosen thinks this should work, because the Vikings only have two defensive backs on the right against the 3 WRs in the bunch.

But Zimmer is just three steps ahead of Rosen here. After the protection call, Kendricks and Stephen Weatherly drop back into coverage, leaving both the RG and the RT blocking just Sheldon Richardson. Meanwhile, Weatherly dropping into coverage enables Mack to follow Fitzgerald’s screen route to the outside. Rosen looks to the screen only to see Mack taking it away, and before he can even look at his next option, Harrison Smith crashes into his blindside for the sack.

The Vikings only rush five, but the way the stunts are set up, both guards end up blocking no one, Smith comes in hot (unblocked), and Rosen’s hot read is taken away by the surprise coverage call. Zimmer gave Rosen no chance.

Harris’ Pick

The Vikings again brought out their double A-gap look with Smith on the edge, and this time instead of resulting in a sack, it resulted in a pick:

Here, the play succeeds less because of the brilliant pressure scheme, and more because of the brilliant coverage scheme. The Vikings initially show seven to blitz, but they ultimately rush only four, and while Hunter nearly gets home on a clever stunt, the main effect of the pressure is to force Rosen into a quick decision.

Prior to the snap, the Vikings appear to be in Cover 1, with Rhodes, Waynes and Hughes in man coverage over their respective WRs and Harris as the deep safety. The Cardinals are running two in-breaking routes from the left bunch formation, designed to carry the slot corner inside and create space for the later-breaking in-route for a first down.

It’s not a bad play call, but the problem is the Vikings aren’t running Cover 1, and Harris isn’t the deep safety. Immediately pre-snap, Smith rotates from showing blitz to playing the deep middle in a modified Cover 3. Harris sneaks down to play the botttom left zone, almost like a robber. The pressure forces Rosen to make a quick read, and he misses that safety rotation. So Rosen throws to Fitzgerarld as he breaks in, thinking he has a first down, when Harris is lurking there for the interception off the disguised coverage.

Mack’s Deflection

The Vikings’ first third-down stop of the game didn’t come from a clever blitz or tricky coverage—just a good play from Mackensie Alexander:

The Vikings initially show blitz with 7, but Barr, Kendricks and Smith drop back into coverage immediately pre-snap. Rosen makes a good read here and finds Fitzgerald with good leverage on a five-step slant, but the pass is slightly high and ahead of Fitz. Mack breaks on the pass well and does a really great job playing the ball and playing Fitz’s hands, deflecting the pass for a three-and-out on the first drive of the game.

Bae Waynes

This next play is also just a great play from the cornerback, with Trae Waynes showing his elite speed to track the crossing route and disrupt the catch point:

The Vikings come out again in a 3-3-5 with all three LBs plus Smith showing blitz in a variant on the double A-gap look. But immediately before the snap, Smith drops back into Cover 2 man, leaving each corner to win their matchup. Waynes does.

Christian Kirk releases inside to evade the press and create separation on his crossing route. Most corners would be in a bind here—very few can disrupt a crossing route after the receiver gets inside leverage. But Waynes shows his elite speed and is able to recover, and moreover he’s able to read the QB while trailing and disrupt the catch point to break up the pass. Just a great play.

Iloka’s Save

The Cardinals only had one third or fourth down play in this game gain positive yardage, and thanks to George Iloka, it also came up short of a conversion:

The Cardinals play it safe on 3rd and 10 from their own 3 yard line and run what looks like a basic iso run. The Cardinals move the TE across the formation, hoping to shake up the Vikings’ gap discipline, and it kind of works: someone (unclear who, maybe Linval or Kendricks) abandons the right B-gap, and David Johnson jump cuts past Richardson and again past Linval to squeeze his way through. Luckily the safeties are there right before the sticks to prevent this from turning into a conversion.

Harris’ Deflection

Ant Harris only played six coverage snaps in this game, but boy did he make the most of them. On this goal line play action run, Harris peels off his man to make the pass deflection and bring up fourth down:

This is a well-designed play by the Cardinals on third-and-goal on the one yard line, with the pre-snap motion to confuse the defense’s gap assignments and a trap block to allow the TE to release upfield quickly. The fullback releases into the flat, carrying Harris and leaving the TE one-on-one against Ben Gedeon. That’s a good matchup to attack.

The only problem is Harris, despite playing man, manages to read the QB simultaneously and peel off his man to disrupt the catch. Just a phenomenal play from the Vikings’ 5th safety.

Leaving Hunter Unblocked Is a Bad Idea

The next play is just a doomed play call by the Cardinals:

Pre-snap, the Vikings appear to be in Cover 1, given that Smith is on the line and Iloka is the only deep safety, and given the man alignments from the other corners. The Cardinals send Christian Kirk on a jet motion and slide the entire line right to account for the pressure, with the idea to get the ball to David Johnson on the screen with two blockers in front.

It doesn’t work for a few reasons. First, the Vikings aren’t in simple Cover-1 man, so what again looked like a numbers advantage on the left side for the screen is actually a disadvantage once Smith and Iloka rotate pre-snap. But second, and more importantly, you can’t just not block Danielle Hunter. Maybe the Cardinals thought the jet motion would throw the defense off, but Hunter explodes off the snap, leaving Rosen backpedaling to try and buy time that Johnson just doesn’t have. Even had the pass gotten off in time, the last-second safety rotation meant that Hughes was there to make the stop. This play call was just doomed from the snap.

Mack Attack

This next play came on 3rd-and-22, so the Cardinals call a screen hoping to just pick up a nice chunk of yards before punting. Thanks to a great read by Mack, they get -2 yards:

There’s plenty going on on this play, but it really boils down to two things: (1) Stephen Weatherly reading screen early and getting his hands up to force a high throw from Rosen, and (2) Hughes reading screen immediately and evading his block to make the tackle for loss.

Barr’s Deflection

This last play was a gutsy call by Zimmer to keep the Cardinals from scoring on third and goal:

The Cardinals come out in 11 personnel, with three receivers right and the tight end out wide. The Vikings appear to be manned up on the right side with Iloka playing centerfield, but Smith brings Iloka into the box to make sure someone is covering the tight end. That’s important, because the Vikings are running Cover 0 here—man up on every receiver, blitz everyone else. Iloka is manned up against the tight end, and once he sees the TE engage Hunter as a blocker, he green dogs and has a clear lane to the QB. Nice pre-snap adjustment from Smith there.

Because the Vikings are blitzing eight, at least one rusher is going to go unblocked, and possibly more will get home as blocking assignments get confused. As Weatherly rushes into his B-gap, Barr does a great job speed rushing upfield, using his hands to clear a path and having the presence of mind to clog the throwing lane. He deflects Rosen’s pass, holding the Cardinals to a field goal attempt on a drive that got to the 8 yard line.

All the plays above showcase why Mike Zimmer is historically effective on third downs: he disguises blitzes and coverages, so QBs can’t rely on pre-snap reads. He designs blitzes that consistently give the pass rush a numbers advantage, forcing QBs to get the ball out ASAP. And then he has the most complicated coverage scheme in the NFL, forcing QBs to make complicated post-snap reads under heavy pressure.

It’s no wonder why it results in sacks and interceptions. It’s no wonder why it resulted in the best third-down stop rate in NFL history last year. And it’s no wonder why the 2018 Vikings third-down defense, at least through the first six games of 2018, is even better.