Last year, the Vikings’ defense allowed only 15.75 points per game, the best figure in the NFL.

This year, the Vikings are allowing 18.75 points in the first half alone.

Last year, the Vikings allowed just 276 yards per game, again the best figure in the NFL.

This year, the Vikings are allowing 382 yards per game, which would have ranked worst in the NFL last year.

What the heck is going on?

Mike Zimmer laid most of the blame on the secondary, some on himself and some on the linebackers

After the Vikings lost 31-38 to the Rams, Mike Zimmer summarized the issue:

Mike Zimmer in his conference call on the defense's mistakes in pass coverage: "Some of it was corners, some of it was safeties, some of it was linebackers, some of it was nickels, some of it was me." — Chad Graff (@ChadGraff) September 28, 2018

That’s a fair assessment, not just of the Vikings’ poor play against the Rams, but the Vikings’ poor play over all four games: it’s mostly personnel issues, mostly the secondary, though occasionally it’s on the linebackers, and the scheme and coverage rules need some tweaks.

But rather than take Zimmer at his word, let’s go through each of the Vikings’ defense’s worst plays in each of the four games to diagnose what is going wrong:

What went wrong in the Rams game?

Everything.

Up until last week, the only game where Mike Zimmer’s Vikings allowed more than 7 yards per play was in the NFC Championship game to the Eagles, where they allowed 7.1 yards per play.

Last week the Vikings allowed 10.1 yards per play. That’s an outlier even among outliers.

But the single-biggest issue was coverage:

Xavier Rhodes, Trae Waynes and Mackensie Alexander each had their lowest-graded games of their careers against the Rams. For comparison, those three players had a game grade of 56.2, 38.1 and 56.1, respectively, in the 38-7 blowout 2017 NFC Championship Game. They graded so poorly they made the NFCCG game look like lockdown defense.

But we can get more granular in assigning blame. Who’s at fault for the Vikings’ worst defensive plays?

Cooper Kupp’s 70-Yard Touchdown

If this play gives you déjà vu, the reason is because it’s essentially the same concept as the George Kittle drop from week one against the 49ers:

Both of these plays look like Anthony Barr’s fault.

Neither of them are on Anthony Barr.

This is a really tough play for defense to defend because it’s really three plays in one: it’s a play-action zone run that gets the linebackers to play the run, it’s a flood concept on one side of the field, and it’s a “leak” to the other side of the field.

Both of these plays resulted in Barr on the TV broadcast looking like he got beat badly in coverage. But he didn’t. Barr’s job on each of these plays is to play the flat / underneath zone. Barr actually does a great job recognizing the play and trying to catch up to Cooper Kupp and George Kittle, but at the end of the day, he’s a 255-pound linebacker matched up against receivers who run a 4.5. He’s not supposed to be matched up on receivers deep.

These plays are really on the secondary. The Rams play appears to be on Sendejo, who makes the understandable error of biting on the flood action and helping the wrong side of the field. The 49ers play is probably on the safeties for the same reason, though there’s a chance Rhodes should have passed off his receiver to cover the leak. Both plays demonstrate how offensive geniuses like Shanahan and McVay can poke holes in Zimmer’s scheme to get receivers matched up on linebackers deep, but then again neither of these plays work if the secondary does their job.

Brandin Cooks’ 47-Yard Touchdown

I could go into detail here about the offensive playcall, defensive playcall, pre-snap motion, but the breakdown in this play is pretty simple—Trae Waynes gets out of his backpedal too late and isn’t able to recover against Cooks’ elite speed:

In fairness to Waynes, this is probably a pass breakup or worse if Goff’s throw isn’t perfect here—Waynes’ ball tracking, recovery and getting his hands up here are all great. But if we’re assigning blame rather than crediting the Rams here, this play is on Waynes.

Cooper Kupp’s 19-Yard Touchdown

To keep things brief, this one’s also on Waynes, though again it’s more about Goff succeeding than Waynes failing:

Waynes is supposed to be playing the deep third of the field, but instead he gets caught peeking at Brandin Cooks, who cuts behind the line of scrimmage into the flat. As a result, Waynes doesn’t get enough depth in his zone, blocks off Hughes (who is in man coverage on Kupp), and opens up a teensy-tiny window for Jared Goff to drop an outrageously good pass to Kupp on the deep crosser in the back of the endzone.

Waynes recovers well here and is just inches away from breaking this pass up, but Goff’s throw is just perfect.

Brandin Cooks’ 23-Yard Reception

That’s enough picking on Trae Waynes. Time to pick on Xavier Rhodes:

The pre-snap motion gets Rhodes in off-coverage against Brandin Cooks, which is a matchup issue for Rhodes, who can struggle in space. Rhodes turns his hips outside, so Cooks drives the stem of his route inside, crossing Rhodes’ face and forcing Rhodes to speed turn at the exact moment Cooks breaks outside. That’s great route running from Cooks, and combined with Rhodes getting hurt and losing his footing, results in Cooks being wide open for the big play.

Todd Gurley’s 56-Yard Reception

The Rams’ pre-snap motion here confirms that the Vikings are in man coverage, as Mackensie Alexander follows his receiver across the formation. Seeing that, Goff checks into this play-action screen call designed to take advantage of man coverage. The play gets one corner (Mack) on the wrong side of the field with the jet motion and gets another corner (Rhodes) on the wrong side of the field with a crossing route. So the success of the play is largely based on McVay and Goff calling the right play against the right defense.

But Kendricks also could have played this better, as he gets sucked in too far on the play action and is late to recognize the screen. Kendricks does a good job sifting through the screen blockers, but then misses the tackle on Gurley. Compounding all this, Sendejo gets blocked in the back, and the refs inexplicably pick up the flag, turning what should have been an 11-yard gain with the penalty into a 56-yard gain.

Robert Woods’ 31-Yard Touchdown

Sean McVay had a lot of brilliant play calls in this game, but this play might have been his best:

As Josh Cohen has explained, the Rams come out on this play in 13 personnel (three tight ends, one back) and line up initially in an i-formation. The Vikings respond by subbing Ben Gedeon in for the nickel corner. Goff then motions the Rams into an empty backfield, with five receivers near the line of scrimmage, which the Vikings respond (predictably, at least to Sean McVay) by checking into Cover 3, bringing Harrison Smith down to deal with the extra receivers and leaving Sendejo to play center fielder.

McVay calls four verts (four vertical routes), which is a Cover 3 killer because it splits the center field safety. Goff looks Sendejo off, leaving Anthony Barr on Robert Woods one-on-one. That’s a matchup no linebacker can be trusted with, and Goff throws a perfect pass to Woods in stride over Barr.

That’s not Anthony Barr’s fault or Sendejo’s fault or anyone’s fault; it’s just Sean McVay and Jared Goff being amazing.

So while Zimmer could tweak his coverage schemes here and there, the biggest reason the Rams had so much success had to do with how well Goff played, and how poorly the Vikings’ cornerbacks played. If you want to read more about what went wrong against the Rams, Arif Hasan has a phenomenal breakdown here, and Matt Fries has some great additional detail here.

What went wrong in the Bills game?

A lot less than you’d think, actually.

Yes, the Vikings gave up 27 points to a fairly talent-poor Bills offense. But a lot of that has to do with the Vikings’ offense and special teams giving the Bills extremely good field position. The Vikings only gave up 292 yards on the game, which in terms of yards per game last year would have ranked 4th best in the NFL.

Still, you don’t give up 27 points without some defensive errors. What needs to be fixed from the Bills game?

Jason Croom’s 26-Yard Touchdown

Croom was left wide open for an easy Bills touchdown thanks to a miscommunication between Mike Hughes and the rest of the Vikings’ defense:

The Bills set up the fake screen here starting with pre-snap motion. Mike Hughes makes a signal that he’s covering the screen receiver (presumably leaving Kendricks to cover the slot receiver), but no one receives that signal and Croom is left wide open. Hughes probably should not have abandoned his assignment without first confirming with the rest of the defense.

Chris Ivory’s 55-Yard Reception

The Bills’ biggest play of the game came on a dump off to Chris Ivory, as Josh Allen was flushed outside the pocket:

As big of a play as this was, the breakdown in coverage is pretty straightforward: Kendricks abandons his middle underneath zone, drawn out by the H-back’s flat route and Allen’s scrambling, which leaves Ivory completely uncovered for 55 yards.

Robert Foster’s 50-Yard Drop

What should have been an equally huge play in the game actually went incomplete after Robert Foster dropped a 50-yard bomb from Josh Allen:

Allen delivers a pinpoint throw here under heavy pressure, but Foster is unable to reel it in. Had it been caught, this play would have been on Mike Hughes, who gets beaten in the foot race on the outside.

Andre Holmes’ 22-Yard Reception

Hughes had a third bad play in coverage, this time against Andre Holmes:

Holmes is running a simple curl route, but Hughes misplays it and initially turns upfield before coming back to the ball, and he then fails to wrap up the receiver, leading to another 11 yards after the catch.

Josh Allen vs. Anthony Barr

Anthony Barr matched up one-on-one against Josh Allen scrambling three times in this game.

On one play, he slipped and gave up a touchdown. On the second play, he was posterized by Allen’s five-foot hurdle, giving up a key third-down conversion. On the third play, he winds up committing a horse collar penalty after being stiff-armed, setting up the Bills’ next touchdown.

Barr’s failures on the Vikings’ defense this year have been greatly overstated (he’s been a very effective pass rusher, helpful against the run and, other than the bad matchups against the Rams, has been lights out in coverage). But there is no doubt that Barr was not ready for Josh Allen’s off-the-charts athleticism.

You can criticize Mike Zimmer for not putting a spy on Josh Allen early in the game, but most of the defensive errors in this game were on the personnel. Against the Rams, Mike Hughes played well while the other corners struggled; against the Bills, Rhodes, Waynes and Mack played pretty well, while Mike Hughes and the linebackers struggled. So far, it’s hard to establish a clear pattern as to what exactly is going wrong.

What went wrong in the Packers game?

The Vikings’ defense bent but did not break against the Packers, surrendering five field goals but only one touchdown over five quarters. With Rodgers’ hobbled, over 75% of the Packers throws came within 10 yards of the line of scrimmage:

The Packers largely dinked-and-dunked their way to 281 passing yards, though there were a handful of critical errors in the secondary that resulted in big plays:

Mackensie Alexander Got Lost Covering Jimmy Graham

Jimmy Graham had two huge receptions in the game. The first one came on third and short and went for 34 yards:

The Vikings run a pattern matching Cover 3. The Packers run a post-wheel combination to the open side of the field, which would beat a traditional Cover 3, except that in pattern-matching Cover 3, Mack (as the nickel back) should follow Graham on the wheel route. Instead, he hesitates and gets caught peaking in the curl flat zone as Graham cuts upfield for 34 yards. Mack’s lapse in coverage turned what should have been a third down stop on the Packers’ 18-yard line into a drive at midfield that resulted in a field goal.

Graham’s second reception came with just sixteen seconds left in the fourth quarter, and set up what could have been the game-winning field goal for Green Bay:

The Vikings are in Cover 4 here, with Mack playing the underneath flat. The Packers are initially running a levels concept to the right side of the field, with Graham on a deep out, but as is often the case with Aaron Rodgers, it breaks down into a scramble drill. Mack again loses track of Graham as Rodgers rolls out to his right, and Graham makes the 27-yard reception and gets out of bounds to set up a 52-yard field goal (that Crosby missed, sending the game to overtime).

Davante Adams’ 9-Yard Touchdown

The Packers’ only offensive touchdown came from Davante Adams matched up one-on-one against Xavier Rhodes. Adams wins with a quick out route and some nifty moves after the catch:

The Vikings run Cover 4, and the three receivers right leave Rhodes on an island against Adams. Rhodes somewhat curiously plays with a lot of cushion and inside leverage, which Adams takes advantage of with the out route short of the goal line. Rhodes then overpursues and is not in a position to make the goal line tackle, and Adams is also able to make Barr miss en route to the TD.

Davante Adams’ 16-Yard Reception on 3rd & 11

The Packers set up Davante Adams for a huge third-down conversion on a deep crossing pattern here:

The Packers motion pre-snap into a bunch formation and run a dagger concept here, with Geronimo Allison on the line of scrimmage running a vertical route to occupy Mike Hughes and Andrew Sendejo, setting up Adams brilliantly on a deep dig. The bunch set forces Rhodes into outside leverage, which makes the play nearly impossible for Rhodes to cover as Adams breaks inside.

Zimmer might be able to tweak his coverage rules against bunch sets here, but the simplest fix would have been for Sendejo to read the play quicker and disrupt the pass. Instead, Sendejo comes in late, and compounding the issues, commits unnecessary roughness with a helmet-to-helmet hit that turns the 16-yard gain into a 31-yard gain.

So the Vikings’ defensive struggles against Green Bay largely came down to personnel, except that again in this game the underperforming defenders came almost at random. Despite playing well against the Bills, Mack really struggled against the Packers. Again, it’s difficult to point to just one player or just one schematic issue; the problem seems instead to be the secondary and linebackers more generally.

What Went Wrong in the 49ers Game?

While the Vikings came away from week 1 with a win, Kyle Shanahan could have easily pulled off an upset thanks to his brilliant play calling. The Vikings struggled against Shanahan’s outside zone/play action-based offense, particularly in play-action passes to George Kittle and Kyle Juszczyk, and we have already seen how the Vikings lucked out with great offensive play calls being thwarted by poor execution. Here are a few other key plays:

Harrison Smith Struggled Against George Kittle

Harrison Smith won Defensive Player of the Week for his performance in this game, but he nevertheless struggled in coverage, giving up one touchdown to Dante Pettis and almost giving up two additional touchdowns to George Kittle:

On the Dante Pettis touchdown, Smith initially makes a good play breaking on Pettis’ post route. But when Garoppolo breaks out on a scramble drill, Pettis cuts upfield, and Smith is late to react, trailing behind Pettis on the touchdown. On the goal line Kittle miss, Smith gets beaten badly at the break as Kittle cuts inside, but Smith gets bailed out by a high, uncatchable pass. And on the deep Kittle miss, Smith is beaten at the release and is unable to recover against Kittle’s elite speed, this time being bailed out by Garoppolo’s overthrow. Had these throws gone the other way, the 49ers could have won this game.

Kyle Juszczyk’s 56-Yard Reception

The 49ers biggest play of the game by raw yardage was this deep shot to the fullback, Kyle Juszczyk:

The 49ers run a post-wheel here and Juszczyk is left wide open on the wheel route for 56 yards (26 after the catch).

From the broadcast angle, this looked like Ben Gedeon’s fault, but the all-22 makes that seem unlikely. Smith and Sendejo occupy deep zones in the middle of the field, the linebackers buzz underneath in their zones, and Rhodes maintains outside leverage—making this look a lot like Cover 4, except that Mike Hughes trails his receiver in man coverage. It’s hard to be 100% certain of the play call and the mistake here, but the simplest explanation is that this was indeed Cover 4, meaning that Mike Hughes should have passed off his receiver and switched onto Juszczyk.

Dante Pettis’ 39-Yard Reception

The biggest play of the game for the 49ers (measured by offensive EPA) came from Dante Pettis matched up one-on-one against Mike Hughes:

Pre-snap, Pettis motions across the formation, signaling Cover 1, with Hughes in off man coverage. Pettis attacks that cushion, bolting his stem into Hughes and giving a great stutter step inside paired with good shoulder and head lean before breaking out:

Hughes made up for these plays (and then some) with a pick six, a run stop and a couple additional pass deflections in this game, but at least on this one big gain, he’s at fault.

George Kittle’s 36-Yard Reception

This last big chunk play came on another genius play call from Kyle Shanahan that set up George Kittle open on a deep dig route:

There’s a lot going on on this play. First, the 49ers are running hurry up, coming off a sweep on their last play and after gashing the Vikings on outside zone all game. Second, this play has two fakes—the outside zone play action, which builds off the previous sweep and outside run run calls, and the Pierre Garçon end around, which occupies Anthony Barr in the flat. Those two fakes also occupy the defensive line reading run, giving Garoppolo time for the deep shot. Third, Marquise Goodwin runs a vertical route to clear a huge space where Xavier Rhodes would have otherwise been.

All that sets up George Kittle with a huge amount of room on the deep dig. Eric Kendricks gets a little lost in coverage, and actually blocks off Mike Hughes from getting a better angle, but rather than blame Kendricks I’m inclined more to credit Shanahan for great game planning.

For a deeper dive on the 49ers game, Matt Fries had two great breakdowns here and here.

So, after 3000+ words and dozens of gifs, what’s the grand takeaway?

The takeaway is essentially the same as Mike Zimmer’s, quoted above. The Vikings’ scheme hasn’t been exposed, and there isn’t any one player who deserves most of the blame. Instead, the defensive struggles are mostly on the secondary generally, particularly the cornerbacks, but the linebackers (particularly Kendricks) and the scheme bear part of the blame as well.

Assigning blame on all of the above plays combined gives you the chart below:

Given the limited sample size of the plays in this article (among other issues), this chart can’t be taken too seriously, but it does help illustrate that in the plays sampled above, the secondary (in blue, with safeties in dark blue and corners in lighter blue) accounts for roughly two-thirds of the Vikings’ defensive struggles, the linebackers account for maybe a quarter, and scheme problems account for the remainder.

Can the Vikings Return to Form, or Is the 2018 Vikings Defense the “New Normal”?

We have four years of evidence—67 games under Mike Zimmer—weighing against these last four games, and evidencing that the Vikings’ recent defensive struggles are more of an outlier than anything else. The 2017 Vikings ranked first in yards allowed, first in points allowed, and best ever in third down stop percentage, and ranked second only to the Jaguars in overall defensive grade and in defensive DVOA. The Vikings returned all the same starters, except that Tom Johnson was replaced by Sheldon Richardson, who so far has been having a career year.

The Vikings players probably didn’t become awful overnight; they’ve just had a few bad games. All-pro players like Harrison Smith or Xavier Rhodes occasionally have a bad game or two, but that doesn’t make them bad players—those bad games are the rare exceptions that prove the rule of how good they are.

The scheme works. That NFL defenses steal more from Zimmer’s playbook than maybe any other defense is a testament to that, and the fact that top offensive minds like Shanahan or McVay were able to poke holes in it in differing ways is a credit to their talent, not an indictment on the scheme.

Some regression from the heights of 2017 would be unsurprising—football is random. The R2 value of defensive DVOA year-over-year is less than 0.1—in plain English, it’s completely unpredictable. But the Vikings didn’t retain everyone then sign Sheldon Richardson only to become the worst defense in football; they’ve just strung together a couple bad games. They’ll bounce back. Hopefully.