49ers film room: How Kyle Shanahan dismantled a Fangio-style defensive scheme in week 4 versus Arizona

Head coach Kyle Shanahan finally got his revenge on Jonathan Gannon.

The 49ers thoroughly dismantled the Arizona Cardinals on defense on Sunday in week 4 by a score of 35-16. The offense had eight total drives. Two were kneel downs at the end of each half. On five of the six other drives, the offense scored touchdowns in methodical fashion.

Purdy was on point and accurate, completing 20/21 passes for 283 yards and two total touchdowns. Christian McCaffrey stole the show however, with four total touchdowns, 106 rushing yards, and 71 receiving yards. Brandon Aiyuk added another 148 receiving yards on six receptions.

The 49ers offense was humming along and showed no signs of slowing down. For a little while, it felt like head coach Kyle Shanahan was sending a message to Jonathan Gannon, current Cardinals head coach and former defensive coordinator of the Eagles, whom Shanahan and the 49ers never really had a chance to showcase what this offense was capable of deep in the playoffs. But no, this wasn’t just sending a message to Gannon.

This week, Shanahan was putting the entire league on notice with how he crafted a gameplan that got seemingly everyone open everywhere on the field, and when it couldn’t, Brock Purdy found ways to fit passes in close coverage to the playmakers. The Miami Dolphins might have stolen the attention with their explosive offense and creative use of motion, but the 49ers have quietly been showcasing their own evolution and doing it to the tune of 30+ points per game.

The Vic Fangio defensive scheme, the league’s answer to the Shanahan tree offenses, may finally be finding its unraveling at the hands of the very offense it was employed to stop. The scheme was the answer to the 2017-2018 Shahanan offense’s ability to create explosive passes. By aligning and playing more 2-deep split safety coverages or showing them presnap, and other pattern match zone coverages, the defense was able to limit explosive gains in the pass and also be able to play to the run by rotating safeties down into the run fit post snap and discourage downfield throws.

Gannon, who spent time with the Eagles crafting a defense in the Fangio mold, with Fangio as a defensive assistant, watched helplessly as Shanahan undressed every facet of it right in front of his eyes, exploiting it’s coverage rules and getting McCaffrey in space against slower edge defenders and linebackers. It should be noted too that the Buffalo Bills thoroughly dismantled the godfather of the system, Vic Fangio’s defense, in a game against Miami on Sunday as well.

How did Shanahan accomplish this? Essentially by knowing the defense’s own coverage rules as well as the opposing head coach knows them. By sending receivers into spaces that corners and safeties would have to occupy because of a series of if-then coverage rules statements, Shanahan was able to get his best offensive weapon in space against other slower defenders who had no choice but to cover him and hope to at least stop the bleeding.

How did they do it? Here’s how.

The 49ers here are in 21 personnel with Kyle Juszczyk and Ronnie Bell split out wide to the right.

The play is essentially a “989” concept (double go routes on the outside with a middle reader route inside). Kittle is the in-line tight end running a quick in breaking route from the other side with McCaffrey on a short motion out of the flat. This looks to be testing the interior edges of the defense and seeing who might cover McCaffrey on passing downs.

The defense is in their base 3-4 personnel grouping. The defensive play call is a drop 8 cover-3 coverage where the nickel takes the slot receiver up the seam as the seam/curl defender and the WILL linebacker takes McCaffrey to the flat.

Purdy drops back looking for Kittle but he's covered tightly. Purdy escapes the pocket and finds McCaffrey cutting back over the middle as his defender steps up toward Purdy. He gets out to him and McCaffrey takes the pass across and down the left sideline for a first down.

On the same drive, Shanahan was able to get McCaffrey matched up on a linebacker while running a choice route from the backfield.

In the red zone, Shanahan is known for calling a 2-way go’s for his playmakers and this gives Purdy a defined read for his first option on a choice route.

The defense is in a 3-deep/3-under zone running a 5-man pressure.

Easy read and an easy quick throw for Purdy. McCaffrey gets matched up on linebacker Ezekiel Turner (No. 47). He reads the leverage with Turner sitting inside so he cuts outside to the sideline where Purdy hits him in stride for a nice quick throw.

There was some commentary later in the week about this play and the fact that Kittle ends up wide open. First, he shouldn’t be wide open. In a 3-deep/3-under zone, one of the underneath zone defenders needs to run with Kittle into the seam, likely the one that passes him off. Purdy can’t possibly know they’d bust their coverage.

Second, Purdy’s first read is McCaffrey on the choice route. It’s open so he throws it to him. That’s how a functioning and efficient offense is run. There’s no issue taking the first open read.

On McCaffrey’s touchdown pass, it almost seems as if the play was meant to go to him by design and looks as if Shanahan knew the coverage he’d get in this area of the field from the Cardinals.

The play call floods the Cardinals red zone quarters coverage with a 3x1 formation and routes that occupy the safeties deep in the end zone. McCaffrey is motioned out to the left on a swing pass and the coverage rules dictate that quarter-flat linebacker match him 1-on-1 on the edge, a clear mismatch.

The defense is in red zone quarters/cover-4 with a “trix” call by the weak side safety, meaning he’ll poach #3 across from the trips side of the formation. Deebo’s corner is “man everywhere he goes” or “MEG,” which pulls another defender out of the zone.

Deebo runs a shallow cross from the left and the weak safety to that side is looking for work across the field. McCaffrey is out in the flat 1-on-1 with linebacker Jesse Luketa (No. 43). With the middle hook linebacker on the far hash, Purdy comes back to McCaffrey and hits a tight coverage throw as McCaffrey is barreling toward the end zone for the score.

Shanahan continued to pick apart the Cardinals coverage scheme all throughout the game and this play was no exception. Purdy had already hit a deep shot to Aiyuk versus this coverage and Gannon tried to disguise it again.

The play is a full field read for Purdy with “Lion” double slants on the left working back to a choice route by McCaffrey on the right underneath a pair of vertical routes.

The defense is playing drop-8 inverted quarters on this play where the deep middle third safety becomes the middle hook defender from depth and the overhang defenders become the quarters safeties.

Purdy drops back and sees no throw to the left on the double slants so he works back to McCaffrey who is covered by a linebacker again. In quarters coverage, the safety and corner to that side have to run with the vertical routes, leaving McCaffrey alone on a slower defender. Purdy is methodical resetting from one progression to the next until he fires the pass at McCaffrey’s chest.

On this last play, Purdy McCaffrey in the flat for a nice 11 gain as from the flat on a swing pass.

The concept to that side again is two verticals with a swing pass to the left to McCaffrey.

The defense is playing nickel cover-9. Cover-9 is a sub package cover-3 where the nickel aligns to pass strength and matches #2 up the seam while the corner takes #1 vertical. The 3-receiver hook linebacker has to push to the final-3 receiver in the pattern.

The linebacker is already at a disadvantage here. With the corner running vertically with Aiyuk the nickel defender running with Juszczyk across the field, there is no one to push right away to the flat to cover McCaffrey. The linebacker, Kyzir White (No.7), has to try to get out to the sideline right away because he has to find and carry the #3 receiver. By the time he catches McCaffrey, he’s already nearly gained 10 yards. 

The 49ers offense was humming along in this game and nothing felt particularly difficult or complicated. Purdy was on time and on target, McCaffrey seemingly found space everywhere and Shanahan was dialed in. The 49ers put the league on notice that they are going to be difficult to contain as the weeks continue on.