Film review: 49ers' flurry of pre-snap motion a unique challenge for Vikings defense

Before every 49ers snap on Saturday afternoon, Vikings defenders will start solving the puzzle of Kyle Shanahan's offense that sends its players east and west before heading north.

San Francisco's second-ranked run game, specifically, is a three-headed speed demon of Raheem Mostert, Tevin Coleman and Matt Breida deployed through mostly traditional designs of an outside zone-heavy team. Unique is the flurry of pre-snap motions run by 49ers players to further spread defenses apart.

"They run the same plays, trying to give you a lot of eye candy," linebacker Anthony Barr said, "and really make you play slower, I think is what it really comes down to."

The 49ers use pre-snap motion more than any NFL team, which has been a pillar of Shanahan's offenses for years, and their repetition and talent have made them excellent at manipulating defenses.

San Francisco's pre-snap movement opens up the passing game, such as end-around motion one way to shift linebackers and open room for a back-side slant. But let's focus on how it fuels a 49ers run game with an NFL-high 23 rushing touchdowns against a Vikings defense that allowed just eight run scores (3rd) this season.

"It's going to happen all the time, I think," Barr said. "Mostly on first and second downs. It's happened pretty often."

1. While Shanahan (as head coach) and Jimmy Garoppolo make their NFL playoff debuts on Saturday, they've been together three seasons. Familiarity creates strong communication, much like the Vikings defense, and may help lead to on-field checks like this first down against Seattle.

The straight-ahead speed of Raheem Mostert (4.34 40-yard dash), and really all 49ers backs, means San Francisco can run outside zone to the field's short side and catch a defense if they're not wise. Left tackle Joe Staley pins the Seahawks' play-side defensive end, leaving Kittle and Juszczyk to bulldoze the linebacker and safety.

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2. Green Bay's offense is the closest the Vikings defense has seen this season to San Francisco, other than their own during practices, of course. The 49ers and Vikings can be credited for helping keep the NFL fullback alive, running the two-back formations more than anybody at 26 percent and 22 percent, according to Sharp Football.

The Packers under head coach Matt LaFleur, who followed Kyle Shanahan from Houston to Washington to Atlanta, are also a heavy outside zone running team — like the Vikings and 49ers — and all three have play-action rates ranking top 12 in the league.

So it's not ideal for the Vikings that Green Bay running backs Aaron Jones and Jamaal Williams racked up 331 rushing yards (5.4-yard average) and three touchdowns in two wins vs. Minnesota. Even removing Jones' 56-yard touchdown, which came without linebackers Anthony Barr and Eric Kendricks on the field, it was a 4.6-yard average. But the Vikings' backbone, limiting explosive plays and making red-zone stops, kept Green Bay to 23 and 21 points in those losses, and could keep them afloat in San Francisco.

The Vikings are much better equipped, in both scheme and personnel, to stop the run than the Seahawks. In the clip below, watch the Vikings defensive line shift with the tight end motion. Once settled, watch how wide defensive end Danielle Hunter (#99) sets, ensuring he's on the outside of the right tackle (remember the Seahawks DE getting pinned inside?). This helps force Jones back inside, from where you'll want to watch the backfield view.

In the backfield view (around :21), two things stand out — Kendricks' balance to mirror Jones and prevent a huge run, and nose tackle Linval Joseph (#98) using his left hand to cleverly hold the Packers center (around :24) and prevent him from blocking Kendricks.

The Vikings' front knows how to subtly disrupt zone schemes.

"They know how to stop it when they have to," Shanahan said. "Zim has got all the calls to put the D-line where they need to put them, to put the safeties where they need to put them. So they've got the scheme to do it, and they've got some very impressive players. Their linebackers and safeties are really hard to block. Their front four is very good."

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Keys to San Francisco's run-game success are again the blocking of Kittle (#85), who gets away with a crafty hold on linebacker K.J. Wright (#50), and Juszczyk, the fullback who single blocks the Seahawks defensive end. Watch how Kittle's pre-snap motion widens the Seahawks defense to the left, further opening the middle where the defensive tackles are driven out. The Vikings have better anchors inside.

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4. The Packers ran a similar fullback-lead counter against the Vikings during the Week 16 loss. Since the Vikings defensive line plays blocks and doesn't shoot gaps very often, this kind of scheme could be problematic. The Packers fullback motions left before the snap, and the Vikings' line leans right to mirror the zone blocking.

Linebacker Eric Wilson (#50), who will be playing the same weak-side role on Saturday, makes the correct read and aggressively fills the alley. But Packers receiver Allen Lazard (#13) delivers a crackback block, freeing Aaron Jones (#33) and the fullback to the outside.

Safety Anthony Harris (#41) makes a quick read and saves an even bigger play on this 7-yard run.

5. The 49ers get receivers involved with 'ghost' motions, mimicking end-around handoffs and/or jet sweeps to distract/widen defenses before and right after the snap. Even though San Francisco is facing a nine-man front, Mostert scores the 13-yard touchdown up the middle in part because of receiver Emmanuel Sanders (#17) ghost motion helping take two defenders out of the picture.

Again, San Francisco doesn't do much double-team blocking as Kittle (#85) handles the defensive end, allowing left tackle Joe Staley to run freely at middle linebacker Bobby Wagner, which stuns him briefly enough for Mostert (#31) to breeze past for six.

The Vikings defense will need to be wary of how the 49ers deploy ghost motions to get key players — like defensive ends Danielle Hunter and Everson Griffen — out of the picture. The Packers used a jet sweep motion back in Week 2 on this 8-yard run, which seemingly prevented Hunter from closing the cutback lane.