clock menu more-arrow no yes mobile

Filed under:

All-22: 49ers pass defense is a problem that doesn't figure to go away any time soon

The 49ers have allowed some gaudy passing numbers over the past two weeks. We go to the tape to break down where things are going awry for Eric Mangini's unit.

Through three games, the San Francisco 49ers have been plagued by a host of issues on their way to a 1-2 start. Perhaps the most glaring, however, is a pass defense that has been absolutely torched in back-to-back games against the Steelers and Cardinals.

San Francisco’s season-opening performance against the Vikings was marked by the near-constant confusion and pressure Eric Mangini’s unit created. Teddy Bridgewater was frequently under duress, and even when he wasn’t, he appeared baffled by a defense that featured a hefty dose of movement and disguise before the snap. Vikings’ receivers were open downfield on several snaps, but Bridgewater was unable to take advantage. The question became: Will a more experienced quarterback be able to exploit the holes left in the secondary by all of that blitzing and pre-snap movement or will Mangini’s designs continue to create pressure and indecision?

Two weeks later and that question has been answered emphatically. Ben Roethlisberger and Carson Palmer each put up gaudy numbers that have left the 49ers near the bottom of just about every relevant pass defense metric. Let’s just throw ‘em all in a table and be done with it:

Stat Value Rank
Pass Defense DVOA 43.6% 29
Passer Rating 111.6 30
ANY/A Allowed 8.9 31
DVOA vs. No. 1 WRs 73.6% 31
DVOA vs. No. 2 WRs 86.1% 32

Beyond the surface-level explanation of "there were a lot of receivers running open downfield," the Steelers and Cardinals beat the 49ers in very different ways. Against the Steelers, Mangini rolled with a similar approach to what we saw in Week 1: Lots of sub-packages and lots of defenders up near the line of scrimmage to try and create confusion. Mangini opted to blitz less frequently, perhaps resigning himself to the fact Roethlisberger would probably beat the blitz anyway, but trying to disguise the intentions of his safeties was ultimately his undoing. Pittsburgh repeatedly threw deep down the sideline and San Francisco’s safeties were unable to recover from their pre-snap alignments in time to help out. That led to the likes of Antonio Brown and Darrius Heyward-Bey running unmolested down the sideline for huge gains.

Determined to not allow the Cardinals to do the same, Mangini switched up his approach. Sub-packages were replaced with base personnel on many snaps. Eric Reid and Antoine Bethea moved back to more typical safety depth more often than not, spending less time near the line of scrimmage. The blitz also returned. According to Pro Football Focus, the 49ers blitzed on an even 50 percent of drop backs in Arizona, up significantly from the 14.8 percent mark in Pittsburgh. The combination of these adjustments, however, opened up lots of space in the middle of the field for an offense that loves to attack the middle of the field. Palmer took advantage of that space time after time, starting with the game’s opening play.

As Fitzgerald motions in tight to the tackle box, San Francisco’s secondary begins to come out of their balanced pre-snap look and rotate to the Cover-3 coverage they’re running on this play. Bethea moves up into curl-flat area. Reid moves toward the deep middle. And Tramaine Brock starts sinking to his deep third.

Once the ball is snapped, you see Palmer’s throwing window start to materialize right away. Bethea fails to get out and redirect Larry Fitzgerald at all. Both inside linebackers, NaVorro Bowman and Michael Wilhoite, are pulled to the left of the offense by Jermaine Gresham’s crossing route. The result is an easy 21-yard completion to Fitzgerald right in that void, setting the tone for what was to come for the rest of the afternoon.

Later in the first quarter, we get another easy Palmer completion to the middle of the field. San Francisco is in different three-deep coverage on this play, Cover 6 or quarter-quarter-half, with both safeties sitting at a depth of about 12 yards. Arizona’s play action pulls up the linebackers, opening a large swath of green grass between the hashmarks for Darren Fells’s crossing route, allowing the Cardinals to get back on schedule with 13 yards after a holding penalty had put them in first-and–19.

On the very next play, Arizona goes back to the middle once more. With both safeties deep to begin the play, San Francisco shows a similar pre-snap look to the previous two plays, this time rotating to a more traditional Cover 3 look after the snap. Assuming you don’t have defenders pulled out of position like we saw on the previous play, one of the best places to attack Cover 3 is up the seam at a depth of 15–25 yards, particularly if you can outnumber the deep coverage with four vertical threats. It’s difficult for the underneath coverage to get that sort of depth on their drops, and as long as the throw is on time, the deep-middle safety can’t cover both players running up the seam. That’s exactly what we get here.

Fitzgerald runs up the left seam past Reid, who is moving forward to get to his curl-flat responsibility. By the time the ball is about to come out, Bethea is still on the opposite hashmark and has no chance of getting over to Fitzgerald in time.

Tally up the damage and Palmer completed 15-of-16 passes between the numbers for 247 of his 311 yards, per Pro Football Focus, averaging an absurd 15.4 yards per attempt. Those numbers include some throws on out-breaking routes that were caught right at the numbers, but you get the idea. The majority of that production came against the 49ers’ base defense, where the Cardinals were routinely able to get Fitzgerald or John Brown running free through linebackers and safeties in the middle of San Francisco’s zone defense.

When the Cardinals did want to attack the outside, they didn’t find much more resistance and repeatedly found success with a single passing concept that was repackaged in a few different forms.

If you start to overplay the routes in the middle of the field that Arizona is so fond of, they’ll come back with the sail concept to the outside. The sail concept is a three-man route combination, featuring deep vertical route (streak or post), an intermediate out-breaking route (deep out or corner), and a short route into the flat. It’s a popular passing concept against three-deep coverages, something the 49ers used heavily in this game.

Fitzgerald is typically the primary receiver when the Cardinals go to this concept. He lines up in the slot here, with the 49ers running Cover 6 out of their base personnel. Fitzgerald sells the inside move, which accomplishes two things: 1) Ahmad Brooks carries him inside, and 2) Kenneth Acker widens and gets extra depth on his curl-flat responsibility because he thinks Fitzgerald is going inside. That’s enough to open a throwing window for Palmer against a coverage that should’ve had a defender (Acker) in that area.

We get some changes in personnel on this play, but the results are the same. With the Cardinals in their two-minute offense at the end of the first half, the 49ers get their dime package on the field. Brown assumes Fitzgerald’s role in the slot and gets loose on the corner route for a pick-up of 22 yards.

Midway through the third quarter, we get Fitzgerald back in the slot and the 49ers back in their base defense to concede 23 more yards on another corner route.


Few adjustments were made throughout the game to prevent Arizona from effortlessly moving the ball downfield on the same few passing concepts. Man coverage was reserved primarily for the red zone, particularly in goal-to-go situations, and when the 49ers wanted to bring pressure, meaning there was little in the way of safety help. And it’s difficult to understand how sitting back in three-deep coverages was the right plan coming into this game. Arizona didn’t run anything different than what they showed in the first two weeks, yet Mangini’s unit looking completely unprepared for what was coming at it.

As long as the pass defense continues to struggle, it puts the 49ers behind the eight ball with everything else they want to do. This is an offense that wants to rely heavily on the run and play action to methodically move down the field and eat up clock. But you’re not going to win many games with that approach when your defense is giving up 30-plus points and 300-plus yards through the air every week. I mentioned it following the Steelers game, but it bears repeating: the slate of opposing quarterbacks the 49ers will face over the next two months is terrifying when you consider what we’ve seen from this pass defense so far. Aaron Rodgers comes to town next week, and provided everyone stays healthy, he’s followed by Eli Manning, Joe Flacco, Russell Wilson (twice), Nick Foles, Matt Ryan, and then Carson Palmer one more time.

Even if the 49ers’ pass defense were to show signs of improvement over the next couple months, whether it be through scheme or execution, the quality passing games they will be facing makes it tough to imagine those subtle improvements will make a notable difference in the end result. And that’s going to make it very difficult for the 49ers to put too many ‘Ws’ on the board before December.