It's safe to say that almost no football fan or expert predicted a complete regression of the 2018 San Francisco 49ers. After closing out the 2017 season on a high wave, the expectation for the first .500 season since 2014 felt inevitable.

Unfortunately, due to multiple injuries and a roster that lacks depth, the team is plagued with fundamental errors on both sides of the ball.

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Today, Pro Football Focus ranks the 49ers' defense dead last with a 53.5-grade. Last season, the team finished with an overall 70.9 defensive grade, though it ranked 29th overall.

The blowout loss to the Los Angeles Rams added more fuel to an already raging inferno, and lead to more questions about if and when defensive coordinator Robert Saleh would be handed his walking papers.

Is it an unproductive defensive scheme or a lack of talent that's lead to the backslide? Below are a few screen grabs from Weeks 6 and 7. Let's try and decipher the mystery together.

Week 6 – 2nd Quarter, 1st and 10 at the GB 33, 15:00



Green Bay Packers' quarterback Aaron Rodgers threw for 425 yards against the 49ers' secondary. There are plenty of factors why, but milliseconds captured in the shot above showcase a major reason. Circled is defensive back Jimmie Ward 'covering' Green Bay Packers wide receiver Davante Adams during the Week 6 contest.

Ward overran Adams' 15-yard out route and ended up four yards past Adams after he made his break. Five-year veterans should successfully defend an out route, or at least challenge the receiver to make a difficult catch.

There's good news though. The 49ers are executing cover three just as it's drawn up. Everyone is covered except Adams.
In this instance, the scheme is sound, but Ward's blatant error is one of many significant lapses committed by the 49ers this season.

Week 7– 1st Quarter, 3rd and 12 at the SF 46, 8:51



Here's the third play of the Rams' second possession. Salah's called a defense that dropped seven into coverage and rushed four defensive linemen.

I'm unclear how seven defenders leave this much open turf, and allow Rams' wide receiver Robert Woods – highlighted in pink – to make a 28-yard play. Further, look at the receiver in the yellow box. He ran an out-and-up that would have gone for six if quarterback Jared Goff spotted him earlier in his progression.

Week 7– 2nd Quarter, 1st and 10 at the LA 47, 12:52



On the Rams' fifth possession, head coach Sean McVay used a Yankee concept which gained 32-yards. Goff found Woods wide open on the left side of the secondary because the 49ers' defensive back did not drop into the deep third of the field.

Rest assured, three 49ers were covering the underneath crossing route. The 49ers' defense has a bad habit of using three men to cover an opponent. It's happened throughout the season.

I'm more confused why the 49ers continue to get beat deep with the Yankee concept, which they've seen a few times already this season. Has Saleh failed to have the scout team run Yankee? Is it not fully explained in the film room?

The continued failure to grasp Yankee falls on the players. They've seen it before, Shanahan has the play in his playbook, and it's a concept that isn't difficult to stop.

Week 7– 2nd Quarter, 1st and 10 at the SF 19, 2:36



Oddly, this is not the same play as we discussed above. It was Brandon Cooks catching touchdown late in the second quarter.

Yet again, the deep third of the field was wide open. Second, safety Adrian Colbert dropped so far into coverage, he was 14 yards away from Cooks. He provided zero help on the play.

Never fear! The 49ers double-teamed Cooks, but Cooks already made his break to the end zone. Neither 49er covering Cooks could recover due to their poor positioning. The 49ers had the right coverage called to stop the score, but with no help from the defensive back, the 49ers gifted the Rams six points.

Week 7– 3rd Quarter, 2nd and 10 at the LA 40, 11:00



The play above is also from Shanahan's playbook. At the top, the receivers ran double dig routes. At the bottom, Woods ran an out route while the outside receiver ran a vertical.

Saleh placed the secondary in man coverage, which forced 49ers' defensive back Greg Mabin to cover Robert Woods alone. Except for veteran Richard Sherman, the 49ers do not have the talent or depth to execute man coverage successfully.

Saleh has to use different coverages throughout the game to keep opposing quarterbacks guessing. Man coverage is a gamble for him, again due to the lack of depth on the roster.

Woods is a top ten receiver, and Mabin is nowhere near the top fifty defensive backs in the NFL. Offensive coordinators and quarterbacks beg for a mismatch of this magnitude, so continue to expect it over the next two months.

Week 7– 3rd Quarter, 2nd and 1 at the SF 39, 10:05





In the first shot, I've drawn up the blocking scheme, run, and the defensive alignment.

The second shot was what Gurley saw as he hit the line of scrimmage. It's hard to blame Saleh for the call when both linebackers end up taking themselves out of the play.

Linebacker Reuben Foster overshot the gap by his third read step. Over-pursuit was an issue for him last year, and it appears it has carried over into his second season.

His aggressiveness is a blessing and a curse. Foster will destroy anyone in his path with the force of a 20-ton locomotive traveling at 220 miles per hour.

When he misses, he's far beyond the ball carrier or his gap responsibility, which leads to significant gains.

Foster has no help from Fred Warner who hardly moved but wound up too far inside to make a stop.

There is plenty of blame to pass around 4949 Centennial Boulevard for the 49ers dismal season. Indeed, coaches are not blameless for the team sinking like a stone, and general manager John Lynch shoulders some responsibility for failing to find better back-up talent. Saleh is calling the right coverage, but he's missing the talent to execute even the most straightforward coverage in his playbook.

Everyone deserves a rebound game, and the 49ers need to use Sundays' game against the Arizona Cardinals to hammer away at fundamentals and execution.

Photos and statistics courtesy of NFL.com unless noted.