How the Chiefs defense beats the 49ers’ rushing attack

For the second game in a row, the Kansas City Chiefs defense is fielding questions about an opponent’s run-heavy game plan.

After their dominant performance in the NFC playoffs, much is being made of the San Francisco 49ers rushing attack — and with good reason. In two playoff games, the 49ers have run the ball a staggering 89 times, gaining 5.3 yards per attempt. That’s a strong commitment to the run — and the Chiefs will need to be prepared for it.

Head coach Kyle Shanahan and the 49ers do an excellent job of mixing up their rushing attack through different concepts, motions and misdirection. The unpredictability in their rushing attack is especially prevalent when operating out of 21 personnel — a running back, a fullback, a tight end and two wide receivers.

In order to highlight the dangerous nature of the 49ers 21 personnel, I’m going to highlight some of the concepts they’ve been running in the playoffs.

Outside zone

In the postseason, San Francisco’s bread and butter has been their outside zone running scheme. While outside zone is a staple in every rushing attack, the 49ers have athletic offensive linemen that effortlessly climb to the second level. Then there is tight end George Kittle — who can seal off defensive ends — and fullback in Kyle Juszczyk, who can easily clear a gap.

Their blocking scheme up front typically leaves large holes for San Francisco’s stretch running game — and their running backs are capable of breaking for big gains; Raheem Mostert, Tevin Coleman, and Matt Breida are all fast and agile enough to make players miss in the open field.

Allowing them holes like we see in this play gets the running back into the third level untouched for easy, massive yardage. So for the Chiefs, maintaining gap integrity will likely be the most important part of their defensive effort against the 49ers.

As we see here, the Green Bay Packers’ alignment does them no favors in maintaining the play side C gap — especially when the box safety is responsible for the fill. When aligned wide, Chiefs defensive ends must be able to set the edge and squeeze an interior gap — and the defensive tackles will have to hold their ground against a double (or knife to the gap) to limit the space and speed the running back can have in the hole.

Defending outside zone is all about building a wall up front and sealing the play side edge. As long as everyone plays their responsibility — remaining gap-sound — the Chiefs have the personnel to do that. But because San Francisco will throw in wrinkles to throw defenders off-balance, that won’t be as easy as it sounds.

Trap blocking with outside zone

The 49ers can find success with their stretch runs even while getting fancy, keeping the defensive front off-balance by running trap blocks up front.

Their athletic offensive line affords them the ability to climb quickly to the second level, getting out of the way of reaching blockers. While the defensive linemen are trying to control the line of scrimmage, mixing in these quick climbs and trap blocks makes it difficult to maintain gap control — and that can lead to big plays.

On this play, Juszczyk’s block on the defensive lineman also plays a key part in springing it. Juszczyk is a dangerous player because he’s a dynamic threat out of the backfield and an excellent blocker in space. But he’s also powerful enough as an inline blocker to kick out a defensive tackle. While Kittle gives the back plenty of room to run by sealing the edge, Juszczyk’s block makes the difference, allowing the right tackle to climb to the second level while still maintaining the gap.

But the right tackle isn’t able to get a good block on the linebacker, ultimately allowing the defense to limit this run to a short gain. If the tackle had executed his block, the running back could have made it to the third level untouched.

In these unique circumstances, individual efforts will be required. Linebackers will have to deconstruct blocks quickly; the climbing linemen won’t give them the space to pursue the back. The defensive ends must squeeze the gap against Kittle, narrowing the hole while the defensive tackles quickly identify (and fight through) trap blocks to disrupt the running back in the backfield.

As shown here, forcing that extra bounce — or that moment of hesitation — can be just enough to keep these lighter, faster backs from getting loose.

Split zone

San Francisco’s rushing attack isn’t just stretch runs and outside zone. They’ll run plenty of inside and split-zone, too.

On this play, Juszczyk is lined up in a split-gun formation — but is responsible for blocking the back side defensive end so that Kittle can climb to the second level. The jet motion from the slot receiver helps freeze the back side linebacker, allowing Kittle to release outside and climb to the second level for the block.

The Vikings defense plays it well. The back side defensive end quickly crashes on the dive, engaging Juszczyk’s slice block in the backfield. The nose tackle commits a hold to stop a climbing blocker and the play side linebacker folds into the play side A gap. Legally or not, every gap is controlled, allowing the Vikings to come up with the stop.

But the jet motion and slice block combination make this a particularly dangerous play. If the linebackers and the back side defensive end take the cheese on the jet motion — which the 49ers implement often enough to worry about — Mostert could hit the play side A gap for a big gain.

Late in the year, Chiefs linebackers have played with good eye discipline — and both Frank Clark and Terrell Suggs have strong play identification skills. With the motion and misdirection the 49ers implement, they’ll need to lean on that discipline.

End around

Just because the 49ers are lined up with two running backs in the backfield doesn’t necessarily mean they’re giving the ball to one of them.

San Francisco routinely implements end around plays in their rushing attack — and they’re able to sell them better than almost any other team. When they see the pulling guard and initial motion from Juszczyk, the linebackers between the tackles will read power run. Juszczyk’s ability to swivel back out after the initial sell — becoming the lead blocker — helps to make it work.

In these situations, on-field communication is imperative. Here, the cornerback sees the end around coming — and the defensive end feels the seal block from the wide receiver. Both players have to let everyone know where the play is developing so the front can react. Even with the Chiefs’ slower linebacker corps, a quick play identification can result in a better angle to the ball carrier — and a stop for minimal gain.

The bottom line

In 21 personnel groupings, the 49ers’ running game is dangerous. Kittle and Juszczyk can be moved around to sell different looks, creating the misdirection that is so prevalent in Shanahan’s game plans — and they can be trusted to execute blocks that other players at their positions cannot.

All of the plays we’ve examined came from the same personnel on the field. So that is what Steve Spagnuolo and the Chiefs defense will know when they set their fronts and adjust their alignments. But schematically, it’s very difficult to gain an advantage when the opposition can execute multiple attacks using the same personnel.

For the Chiefs defense, film study is the key. They will need to be able to identify plays a split-second earlier, trust the front to stay gap-sound and execute their assignments. When the offense gets just the right call against the wrong front, individual effort to beat a blocker could make the difference between a second-and-medium and a touchdown.

San Francisco will run the ball with lighter personnel, but they will have 21 personnel on the field for around half of their snaps — and what they can do with this personnel grouping is very dangerous. The Chiefs can definitely find ways to stop it — particularly if the Kansas City offense can score early — but they’ll have to be at the top of their game.

Coming soon: a look at San Francisco’s passing attack.