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How the Chiefs defense beats the 49ers’ passing attack

Let’s take a look at how the 49ers utilize heavy personnel in their passing attack — and how the Chiefs defense can control it.

NFC Championship - Green Bay Packers v San Francisco 49ers Photo by Michael Zagaris/San Francisco 49ers/Getty Images

Earlier this week, I took a look at the diverse rushing attack the San Francisco 49ers possess — and how the Kansas City Chiefs could slow it down. But San Francisco wont just run out of their 21 personnel; they’re going to throw from it as well.

I’m going to close out my preview for this side of the ball with a look into the concepts that Kyle Shanahan and the 49ers utilize when passing the ball out of their heavy personnel — along with some notes on where the Chiefs can hope to slow them down on Sunday.


Like all good rushing teams, San Francisco has a potent play-action passing game. Jimmy Garoppolo is arguably at his most comfortable in play-action, relying on the fake — and Shanahan’s excellent play design — to create throwing lanes and space in the secondary.

The 49ers use their play action most effectively out of their 21 personnel — largely due to the varied alignments they use for tight end George Kittle and fullback Kyle Juszczyk. On a play-to-play basis, their ability to show run-heavy personnel — and still have an effective passing game — is what makes San Francisco so dangerous.

As we see here, Juszczyk regularly chips blockers from an H-back alignment. That helps slow the pass rush, allowing for longer-developing routes to be run. His kick-out into the flat helps pull the linebacker forward, creating a wide throwing lane for Garoppolo to hit Kittle on the deep out.

It’s difficult to line up in man coverage against Kittle. It’s even more difficult to do so when your pass rush is slowed by chipping blockers. Shanahan is excellent at buying that extra split-second to spring the route. That means tight coverage that disrupts timing will be imperative to help pass rushers get home.

Max-protect play-action shot

The 49ers hit on their fair share of explosive plays — and they can do it on three-man routes with maximum protection.

Earlier, I showed San Francisco’s willingness use Kittle as a run-blocker against a defensive end. They’re not afraid to do it in pass blocking, either.

Here, Kittle is tasked with blocking Cameron Jordan one-on-one — which is no small ask for a tight end. Garoppolo sells the play-action and the back stays in to block. The play-action — and Juszczyk leaking into the flat — pull the second-level defenders forward. The dual dig routes create conflict for the deep safety, who opens his hips toward the number two receiver. Garoppolo sees the safety open his hips, hitting the follow in yet another large throwing lane.

Against the 49ers, linebacker depth could be a very big problem. The Green Bay Packers opted to keep their linebackers deeper to prevent some of these gaps in coverage. The 49ers countered by running the ball. Other teams have played with more traditional alignments; against them, San Francisco exploited the high hole in coverage.

So for the Chiefs defense, it will come down to quick play diagnosis — and trust while passing off receivers. During the the Chiefs’ defensive turnaround, we’ve seen Tyrann Mathieu and Bashaud Breeland pass receivers quickly and then sink to rob routes. With Garoppolo’s tendency to throw to the seam — between the hash and the numbers — a quick sink from Chiefs defenders might cause him to pull the ball down or throw a tide-turning interception.

Late motion

Whether the Chiefs are in match zone or man coverage, they’ll have communicate well, reading offensive alignments to figure out their coverage assignments. But Shanahan loves to toy with the read just before the snap to add a layer of confusion to the mix, compounding any errors that might occur.

In this play, the 49ers are in their 21 personnel, aligned in a split-gun formation. They identify man coverage by motioning Juszczyk to the sideline. This widens the split between the two off-ball linebackers who remain in the box to cover the gap left behind. Just before the snap, Garoppolo motions the back to the field, pushing the linebacker out even further. After the snap, the running back kicks out into the flat, pulling the linebacker forward. This creates space in the middle of the field for a single-read slant that picks up nine yards.

These are the types of plays where match coverages can thrive. Forcing the linebacker to cover down to the flat opens up a too-easy throwing lane. By matching the distribution, the linebacker would sink to rob the slot receiver while passing coverage responsibility to the cornerback.

Shanahan often dials up these “easier” concepts, creating extra space and a rhythm for his quarterback. Switching up coverages — and keeping linebackers from being stretched to the flat against speedier running backs — could force Garoppolo off his first read, allowing the rush to disrupt his rhythm a little more.

Hot routes

Like most quarterbacks, Garoppolo struggles with pressure in his face — and can make poor decisions. But even when San Francisco has heavy personnel on the field, lining up and blitzing him isn’t always the best option; Shanahan does a fantastic job designing clever checks that spread out man coverage when the defense is blitzing.

Here — against the Minnesota Vikings’ man-free coverage — Garoppolo motions Juszczyk to H-back from the I formation, while the running back starts moving to the flat early. The Mike linebacker has to run to the flat with the running back, opening up the whole middle of the field. The slot receiver beats his man in coverage — and the 49ers beat the blitz.

The Chiefs have a defensive coordinator who likes to blitz — and to keep Garoppolo guessing, they’ll need to do it. Steve Spagnuolo will have to get creative with his zone blitzing scheme, dropping his defensive ends and tackles into throwing lanes to prevent easy yardage like we see here. We’ve seen Spagnuolo safety blitz from condensed splits like this one, so a Tyrann Mathieu blitz off the edge — while dropping the back side defensive end — may help mix up the pressure packages and result in sacks.


With their heavy personnel, the 49ers aren’t afraid to go to an empty backfield. This allows them to stretch out the base defense, forcing linebackers who may be more uncomfortable sinking in zone and robbing crossing routes to do exactly that. That’s what we see in this play.

For most of the season, the Chiefs haven’t trusted their base defense in coverage. In some situational downs, Spagnuolo has used lighter boxes against the run, bucking the heavy-versus-heavy convention that most coordinators utilize. Against the 49ers 21 personnel, that might not be as easy; it almost requires the extra run defender at all times.

Spagnuolo is likely to do everything in his power to protect his linebackers from being exposed in coverage. But the linebackers themselves will have be unified, trusting each other in their zone drops and passing receivers from one zone to another.

In big moments, we’ve seen linebackers step up, making plays in coverage they don’t typically make — see Reggie Ragland in the 2019 AFC Championship game. The Chiefs might need a few of those to help turn the tide.

The bottom line

On Sunday, everybody in the building will know the 49ers are going to try to take advantage of the Chiefs’ linebackers out of their 21 personnel; they’ll try to stretch the field in the running game — and create space in the passing game — against the second-level defenders.

You know it. I know it. And Steve Spagnuolo knows it, too.

But Spagnuolo has done a masterful job getting the most out of this group — and I don’t expect that to stop on Sunday. Throughout the year, Ragland, Damien Wilson and Anthony Hitchens have been tested by speed, play-action and exotic motion.

The Packers exploited Chiefs linebackers in coverage — but Spagnuolo adjusted. Through the middle of the season, teams pounded the rock with stretch plays — and Spagnuolo adjusted.

He’s been in this same situation before — with a slower linebacking corps and a secondary group that is better than the sum of its parts. Using them, he was able to slow down (and beat) an all-time great New England Patriots offense in the Super Bowl through an excellent game plan featuring diverse pressure packages and the disruption of timing routes. This Chiefs team may not have the front line that the New York Giants did — but they’re not going up against the same quality of offensive line or offensive firepower, either.

San Francisco is going to put points on the board; they’re a very good football team. But the longer the game stays close — or in the 49ers’ favor — the more we’ll see the Chiefs using their heavy personnel and the concepts I’ve highlighted this week. Ultimately, if the Chiefs can get early stops — and put points on the board — the 49ers’ dynamic 21 personnel and play-action passing game will be rendered useless.

Spagnuolo will have something to counter Shanahan’s offense. It might be after the first quarter or it may be after halftime — but we’ll see it.

This moment is why the Chiefs hired Steve Spagnuolo. Let’s see if he can prove it was the right decision.

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