49ers Film Room: How and why the 49ers defense is the top unit in the league
How DeMeco Ryans has built the league's best defensive unit.
The 49ers defense is, once again for the second time in four seasons, a top 5 defense in the league. And they’re in a position they haven’t relinquished since 2019. Their worst placement as a unit was 2021 when they ranked 7th in the NFL in Football Outsiders DVOA. In 2020, without Nick Bosa for the entire season and without Richard Sherman for most of that season, the defense was ranked 6th in the NFL.
Sustaining that kind of performance for four straight years is no easy task, especially since it’s happening under two different defensive coordinators. No team in the last four seasons has placed consistently in the top 7 of DVOA on defense except San Francisco. Buffalo and New England are the only other teams to do it three times since 2019.
In 2022, the 49ers are ranked 1st in Football Outsiders DVOA and 1st in defensive EPA per play. The defense boasts the 3rd lowest drop-back success rate and the 2nd lowest run success rate. Per Sharp Football Analysis, “A play is considered successful when it gains at least 40% of yards-to-go on 1st down, 60% of yards-to-go on 2nd down and 100% of yards-to-go on 3rd or 4th down.” That means the 49ers are not letting teams pick up those yards 65% of the time in the run game and 60% of the time in the passing game.
How are they doing it? Through scheme and just flat out having elite players nearly everywhere but with two players in particular: Nick Bosa and Fred Warner.
Nick Bosa and the speed rush front
The 49ers have had a dominant defensive line since drafting Nick Bosa second overall in the 2019 NFL draft. They have been able to plug and play other linemen around him and that have been able to free him up to get favorable rushes or that have created 1-on-1’s for other defensive linemen to excel. This is the story of the last three and quarter seasons but is magnified now with how dominant they have been.
Nick Bosa is a strong candidate for Defensive Player of the Year and sitting on 15.5 sacks this season so far with four games left to play. An 18-20 sack season is not out of the question at this point. Per Pro Football Focus, he has 70 total pressures (15 sacks, they do not count half sacks, 22 QB hits, and 33 hurries). His pass rush productivity rate is 10.5, a measure of how often he’s generating pressure per snaps played, ranked 10th in the league among edge rushers.
Although Brandon Thorn of the substack Trench Warfare (hyperlinked below) does not have his week 14 or week 15 data available yet, as of week 13, Bosa ranks 4th overall among edge defenders in his “true sack rate” score, a measure of the degree of difficulty of each sack recorded each week.
Ranks like these are useful in determining where players stack up but what cannot be seen in these metrics is how they are utilized in a given pass rush situation and what it does for other players next them in the defensive front.
To get Bosa 1-on-1 or get favorable match-ups for him, they often employ the use of the 3x1 overloaded defensive front with three defensive linemen lined up to one side of the ball and single pass rusher to the opposite side. They usually mug the single pass rusher side A-gap with linebacker Fred Warner (second play).
Here the 49ers are in a 3x1 overload front with Bosa lined up as the single pass rusher to the left side of the defense (offense’s right). On the right side of the defensive line, the 49ers have their overload side, three defensive linemen consisting of two defensive ends and one defensive tackle. They are all lined up to their right of the center.
On this 3rd-and-6 early in the game versus Miami, they are only rushing the four defensive linemen at Tua Tagovailoa. The overload side draws the half slide to the left with three blockers in pass protection but Charles Omenihu is the penetrator on the B-gap stunt here and draws block of the right guard. Bosa, the looper on the stunt, actually gets chipped into his rush, aiding him into the A-gap where he gets a free run at Tua.
Tua has to rush the throw with Bosa barreling down on him and linebacker Fred Warner is able to tip the pass away over the middle.
On this sack on Tua in the second quarter of the week 13 game versus Miami, Bosa lined up on the overload side of the front on the outside shoulder of the left tackle in the 5-technique defensive line spot.
Bosa is the looper here rushing from the 5-technique with Arik Armstead (No. 91) “spiking” the A-gap as the penetrator and Charles Omenihu (No. 94) has the contain rush outside in the B-gap case the quarterback tries to escape the pocket.
Samson Ebukam (No. 56) and Fred Warner also rush on this play and occupy the backside away from the three-man slide to the left.
Armstead's inside move to the A-gap draws the Dolphins center to him while Bosa loops around the rushers from the outside into the A-gap untouched for the sack. Since Warner and Ebukam draw 1-on-1’s here, Bosa is able to get free up the middle where he runs through uncontested for the sack.
Patrolling the center of the field
The front four of the defense isn’t doing this all by themselves. The back half of the 49ers defense in coverage has also been elite at erasing reads and eliminating receivers, enabling the pass rush to get home and generating turnovers themselves.
One way the 49ers put the clamps on opposing passing games is through the use of cover-6. While predominantly playing their base cover-3 and cover-1 on most downs this season, the 49ers will align their coverages to a more 2-deep shell on high leverage passing downs.
Cover-6 is a combination coverage with cover-2 away from the passing strength and cover-4 or quarters to the passing strength with the nickel aligned to that side. Even though the coverage is played from a 2-deep safety shell, the coverage is still considered a 3-deep/4-under zone with match principles.
The underneath defenders’ responsibility align with the back end coverage and use match principles to fill in the gaps. For example, the “QTR Flat” defender (quarter flat) would chase the flat route out to the perimeter but would carry them if they go vertical because the safeties are playing over the top of the vertical routes or deep in breaking routes.
The vertical hook defender fills in the void in the cover-2 side and the “3 receiver hook” or “middle hook” defender (Warner) carries the third receiver into the pattern.
Warner has the middle hook responsibility here and would cover or run with any intermediate in-breaking or crossing route. He passes off the inside seam route to the quarters coverage defenders while visioning and gaining depth on the dagger route over the middle. Tua rushes the throw over the middle and tries to layer over the top of Warner to former 49ers receiver Trent Sherfield but Warner leaps and knocks the pass out of the air off its trajectory.
Even when he isn’t being targeted, Warner still erases the middle of the field and enables the pass rush to get home.
The defense is in cover-1 behind a 5-man pressure with Warner initially lined up in the B-gap. The 49ers do rush Warner here on occasion from the overloaded front to create 1-on-1 for the overload side to be able to get pressure up the middle.
However, on this play Warner is dropping into man-to-man coverage on Julio Jones (No. 8) with a bracket over the top from safety Tashaun Gipson (No 31). The 5th rusher is Dre Greenlaw.
Warner flies out to cover Jones on the deep crossing route and runs with him step for step. Quarterback Tom Brady is initially looking there but has to come off the read because of the bracket on Jones by Gipson and Warner. The pass rush, led by Bosa, almost gets home but Brady is able to throw it away just in time.
How DeMeco Ryans disguises coverages
On offense, head coach Kyle Shanahan’s philosophy is to make everything look the same in the run game and play action passing game. It’s how they generate explosives and sequence play calling. The blocking looks the same post snap on the run as it does on the play action pass.
On defense, that philosophy has carried over. Often times, on high leverage downs, third down in particular, the 49ers pre-snap coverage shell does not distribute the same way post-snap. Two deep safeties frequently rotate to single-high and sometimes single high rotates to two deep safety coverage. On other plays, the coverage post snap could like zone but distribute as man coverage.
Against the Saints, Ryans often disguised his zone and man coverages by hiding them in the alignments of the coverage defenders. It’s becoming more common in the NFL to play man-to-man coverage from zone alignments and to play zone coverage from man-to-man alignments.
Here is a standard disguised cover-3 buzz call (nickel cover-9 with the nickel aligned away from the safety buzz rotation). Cover-3 buzz is weak rotated safety coverage away from the passing strength to allow the weak side safety to play any crossing routes coming from the strong side. Usually, the 49ers play 3-buzz when offenses line up in some form of 3x1 trips formation.
The Saints are running in-breaking routes here from the slot to the right and the single receiver side. This would be a good call versus a 2-deep safety coverage post snap but the safety rotation down by Hufanga to the weak hook zone inserts another defender into the throwing windows, allowing them to disrupt the timing of the in-breaking routes. The result is quarterback Andy Dalton having to check down.
On another play from the same game, Ryans has a cover-1 robber coverage called. Robber is the same as buzz but is man-to-man coverage rather than zone.
Hufanga drops down to the intermediate level of the field to rob the middle of any crossers or in-breaking routes. The defense is man-to-man with zone alignments (off coverage corners).
The Saints actually have a good single high beater called (doubtle swirl) here where they run a middle read route behind the safety dropping down to rob the middle of the field. Gipson shades over to the trips side and gets caught with Chris Olave streaking up and across the middle of the field. The pass falls incomplete.
The difference in both of the above coverages is where the defenders eyes go. In man coverage, you can see the eyes go to the receiver they have to cover. In zone, you can see the defenders visioning the QB and key in off the route distribution.
Watch Warner pass off anything that goes vertical and watch the corners alignment. If the corners are turned more inside at a 45 degree angle, the coverage is likely zone. This allows them to vision the quarterback and receivers a bit easier than if they were head up over their receiver.
If they’re more head up they’re reading the release of their receiver and playing man coverage. They cannot vision the quarterback as well from those alignments though playing with off-coverage should help that a little bit. The idea is to confuse the offense and make them second guess even if they have an idea of what is coming.
On one coverage rotation in the third quarter from 2-deep to pre-snap to cover-3 buzz post-snap, the 49ers were able to defeat the route distribution by inserting into the throwing lane where Brady wanted to go and forcing him into an errant pass as he progressed through his reads.
The defense is playing cover-3 buzz post-snap but the Buccaneers had a 2-deep safety coverage beater called for the #2 receiver in the trips.
The Buccaneers play is designed for countering a cover-2 with bailing safeties to the deep halves of the field.
Since the buzz rotation occurs after the snap, Brady reads it out to see if he has a throw to the slot #2 receiver. But the buzz rotation inserts another defender and compresses the throwing windows forcing Brady to come off the route and look elsewhere. He’s rushed into an errant throw and throws an interception.
Outlook
These are just some of the ways that DeMeco continues to build the best defense in the league. It helps having two elite talents on the defense too but as you can see from the clips above, it’s never always one person and is instead a collaborative effort by the whole defense. The coverage aids in the rush, and the rush aids the coverage. What’s most important is how the defense is structured and how the two units work together in tandem to be the best defense in the league.