49ers Playbook, Week 12: Cover 3 and Cover 4 pattern match

SANTA CLARA, CA - NOVEMBER 26: Quarterback Russell Wilson #75 of the Seattle Seahawks is tackled by Cassius Marsh #54 of the San Francisco 49ers at Levi's Stadium on November 26, 2017 in Santa Clara, California. (Photo by Lachlan Cunningham/Getty Images)
SANTA CLARA, CA - NOVEMBER 26: Quarterback Russell Wilson #75 of the Seattle Seahawks is tackled by Cassius Marsh #54 of the San Francisco 49ers at Levi's Stadium on November 26, 2017 in Santa Clara, California. (Photo by Lachlan Cunningham/Getty Images) /

This week’s installment of 49ers Playbook looks at how the 49ers were able to use Cover 3 and Cover 4 pattern match to limit the big pass play against the Seattle Seahawks in Week 12.

Coming into the Week 12 game against the San Francisco 49ers, Seattle Seahawks quarterback Russell Wilson ranked second in deep-passing attempts, going 21-of-59 for 723 yards, five touchdowns, one interception and a 104 passer rating, according to Pro Football Focus.

A deep pass is a pass that travels 20 yards or further in the air.

Last Sunday against the 49ers, Wilson completed three of seven passes for 61 yards, zero touchdowns and one interception and a passer rating of 74. For the season, over two games, the 49ers held Wilson to a 3-of-8 mark, 61 yards, zero touchdowns and one interception — a passer rating of 65.1.

San Francisco 49ers
San Francisco 49ers /

San Francisco 49ers

Contrast that with 2016, where Wilson completed seven of 11 passes for 270 yards, one touchdown and a passer rating of 137.5, per PFF.

So how were the 49ers able to finally limit the big-play potential of one of the best deep passers in the league? By playing sound Cover 3 and Cover 4 pattern-match principles, staying in their rushing lanes and dropping seven or eight guys into coverage.

The 49ers put Wilson under pressure just 25 percent of the time (10 of 39 dropbacks) and the 49ers did not record a sack.

Let’s go to the film and see what they did in Week 12.

In the first quarter, the Seahawks lined up in an empty set with five wide, four to one side, and one single receiver on the other. Wilson motioned a receiver to the right to create a 3-by-2 look, still in empty.

The Seahawks run a double curl-flat concept to the bunch side of the formation with a combination out route and fade to the right. The 49ers are in their dime package with Cassius Marsh and Elvis Dumervil as the edge rushers.

The 49ers are playing a Cover 3 pattern-match coverage. Briefly, pattern-match coverage is a way for a defense to disguise their coverage and only play man to man on any routes that come into its zone.

Defenders will match deep routes to the outside or sit on anything that comes into their zone. Inside defenders will follow routes into their zone or pass of crossing routes to other inside defenders.

At the snap, free safety Antone Exum rotates to the bunch side, while corner Dontae Johnson will take any vertical route downfield, unless a receiver occupies the flat. Then he will sort of sink into a boundary flat zone. The opposite corner, Ahkello Witherspoon, takes the deep route all the way downfield, while the flat defender matches the out.

Safety Eric Reid and linebacker Reuben Foster match up on the inside-curl routes, since those routes occupy their zones.

Marsh and Dumervil maintain their outside rushing lanes while DeForest Buckner and Solomon Thomas get pressure up the middle to force Wilson off his spot.

Wilson has nowhere to rush outside, so he tries to escape up the middle. But Buckner is able to defeat his man and catch Wilson, who tosses an errant pass before he gets sacked. The pass sails right through Johnson’s hand on the sideline and falls incomplete.

On the next play, the Seahawks are again in an empty 3-by-2 formation, this time with an inline tight end to the two-receiver side. The 49ers are showing a Cover 2 shell.

At the snap, the 49ers defense rotates to a Cover 4 (quarters) but also adds an underneath-hook zone defender by dropping defensive lineman Sheldon Day into coverage to take away any in-breaking routes over the middle:

Cover 4 is a four-deep, three-under zone defense that uses man-to-man principles (pattern matching) while creating opportunities for both the free and strong safety to double (or “bracket”) the No. 1 wide receivers.

The corners play man to man on the outside receivers with outside leverage and play aggressive on anything out breaking 10 yards or deeper. Anything in breaking before a depth of 10 yards will be handled by the flat defenders, who then match the receiver man to man.

Corners run with the receivers on any vertical routes (10-plus yards).

The safeties will either bracket the outside receiver with the corner if the No. 2 inside receiver runs any shallow crosser or out route. If the inside receiver gets vertical, then the safeties will cover man to man on seam or deep cross, dig or hook route.

As Day drops into a zone, Tank Carradine and Thomas rush from the edge with Buckner getting pressure up the middle. The three-man rush is able to get pressure on Wilson, due to the eighth man in coverage and nowhere to throw.

Wilson easily escapes the pocket and avoids would-be sacks by Thomas and Buckner. The coverage again matches the receiver routes that come into their zones, and Wilson cannot find anyone to make a play too.

Before he is taken down by Buckner, he tosses the ball out of bounds. A combination of the extra man in coverage (Day) and sound matching principles enables the 49ers to again come up big and prevent the big play.

The final play again demonstrates the soundness of the basic Cover 3 scheme in coordinator Robert Saleh’s defense to take away the big play.

The Seahawks show a trips set to the right with tight end Jimmy Graham as the lone receiver to the left and running back in the back field. They are running a curl-flat concept to both sides with a spot route over the middle. The 49ers show a Cover 3 shell.

At the snap, the corners sink into three-deep zones with the deep curls and stay man to man when Wilson scrambles.

The flat defenders widen with the flat receivers, while linebacker Brock Coyle passes off the inside receiver to Foster, who sits in the zone with the spot route and takes him downfield when Wilson scrambles.

The pass rush again features Carradine and Thomas on the edge, with Carradine as the LEO and Thomas the big end. The interior rush by Earl Mitchell and Buckner creates pressure on Wilson who tries to escape to his left but sees Thomas there in his lane, forcing him to toss the ball out of bounds.

The 49ers defense played sound football throughout the course of the game before being worn down late in the third quarter, as they have for many games this season. They have been able to get production from the front seven defenders more than any recent season, especially as the playbook incorporates more complex assignments for the defenders.

Next: Garoppolo and the Debut of 49ers Quarterbacks

Being able to limit the ability of Wilson to scramble and make big plays should give the rest of the league a blueprint for how to do it. For now, it seems the 49ers have been at least able to do what none one else really has.

And that is something to build upon.