Nick Bosa, Fred Warner and the 49ers defense: A midseason efficiency evaluation (2024)

The 49ers’ defense opened this season at a blistering clip — through five games, the unit was surrendering less than nine points per game — before injuries took a heavy toll.

Bad news first: The 49ers’ defense leaked oil in games against the Falcons, Chiefs and Rams to close the season’s first half. The good news: Their problems didn’t extend beyond halftime against L.A. The defense fixed its shaky start with a resounding finish, holding the Rams to only 58 total yards of offense after intermission.

Perhaps even more significantly, the 49ers didn’t report a single injury after their win, enabling further defensive recuperation over the bye week. When the 49ers return to action on Sunday against the Chargers, they might field a unit that welcomes back numerous key pieces. Potential returns include cornerback Jason Verrett, linebackers Azeez Al-Shaair and Dre Greenlaw and defensive lineman Arik Armstead.

The 49ers’ defense, as outlined in the first part of our midseason review, currently ranks No. 9 DVOA — No. 4 against the run and No. 14 versus the pass. A return to at least the top five over the season’s back nine games can start with the defensive line, which adjusted well to L.A.’s screen-pass attack down the stretch. That’s a good sign for the 49ers because more screen passes are certainly coming their way.

Below are the 49ers’ D-line usage clips and pass-rushing splits at the halfway mark. Pass-rush productivity is a score that combines sacks, pressures and QB hits. It’s calculated by Pro Football Focus.In the tables below, darker blue signifies performance further above the NFL average while darker red denotes performance further below it.

Edge rushers listed above the horizontal line and defensive tackles are below it. Players are ranked against others at their respective positions. The 49ers released Akeem Spence after their most recent game.

The 49ers’ adjusted sack rate of 8.5 percent ranks No. 7 in the NFL.

Nick Bosa (8 1/2 sacks), Samson Ebukam (3 1/2 sacks), Charles Omenihu (3 sacks) have formed one of the most productive edge-rushing triumvirates in football. Drake Jackson (3 sacks) is also a threat, and the 49ers expect the rookie to grow more productive with more NFL experience.

There’s added pressure on the 49ers’ cadre of edge defenders to deliver because the team’s interior pass rush has lagged. All of the 49ers’ defensive tackles have logged below average pass-rush productivity grades.

Perhaps Armstead can give the interior rush a boost if and when he does return from his foot and ankle injuries, but that’s anything but a guarantee given the seemingly lingering nature of his issues and their supposed impact on his pass-rushing numbers this season.

A reasonable expectation from Armstead, assuming he does return: impactful interior run defense. There’s plentiful evidence indicating that Armstead’s presence at tackle has been a primary key for the 49ers’ run defense, and that’s unlocked pass-rushing opportunities for the unit’s deep stable of edge rushers. The D-line succeeds and fails as a unit, with an operative variable being its efficiency against the run.

The 49ers speak often of earning the right to rush the passer. They accomplished that by smothering L.A.’s run and screen game. Defensive coordinator DeMeco Ryans channeled much of the effort to combat the latter through star linebacker Fred Warner, who’s delivering possibly his best season to date.

Warner, like essentially every one of his defensive teammates, struggled in the 49ers’ blowout loss to Kansas City. He looked confused in run pursuit and was ineffective in coverage. But that was decidedly not the case down the stretch of the 49ers’ most recent game. Warner delivered with blistering speed, especially when Ryans dialed up a series of blitzes over offensive guard in the second half.

That proved to be a course-correcting adjustment. Warner registered three pressures and a sack. He’s delivered eight well-timed pressures on 20 blitzing opportunities this season, good for the best pass-rushing productivity clip of his career.

If the 49ers have to continue manufacturing interior pressure, Warner is proving to be up to that task. He’s also tackling much more efficiently than ever before and allowing the lowest catch percentage in pass coverage of his career. Warner’s successful coverage of Rams’ star wideout Cooper Kupp on a critical red-zone play in Week 4 was one of the 49ers’ most impressive defensive plays of the season.

Speaking of pass defense, the 49ers have logged good marks there on the back end — but there’s a noticeable hole that they’ll hope to ameliorate with Verrett’s return.

Cornerbacks are listed above the horizontal line and safeties are listed below it. Only defensive backs who’ve logged the 100 snaps necessary to qualify are listed on the table.

Emmanuel Moseley’s ACL tear in Week 5 was a major blow to a 49ers’ defense that had been delivering airtight coverage at both outside cornerback spots. The team’s hope is that Verrett can effectively replace Moseley opposite Ward, who’s been solid across the board. Ward has been especially good in run support. He’s PFF’s top-graded DB in run defense and hasn’t missed a single tackle all season.

As of now, Deommodore Lenoir is the 49ers’ top option behind Ward at outside cornerback, having moved over from the slot to fill that vacancy. But Lenoir hasn’t been great on the outside or in the nickelback position. The 49ers have insisted on playing Jimmie Ward, traditionally a safety, in the slot corner spot over the past two games and that might continue even if and when Verrett returns and grabs an outside cornerback role.

That’s because the 49ers are generally pleased with the safety play that they’ve seen from both Talanoa Hufanga and Tashaun Gipson Sr. Hufanga’s biggest issue is that he’s missed 13 tackles, but the team has been happy that both he and Gipson have been well-positioned in both pass coverage and run defense.

Nickelback is a bigger issue than safety for the 49ers — it might be the secondary’s onlyglaring issue if Verrett returns successfully — and the team believes that Jimmie Ward is its best available coverage weapon, especially once the cast comes off his broken hand in the coming weeks.

Ward’s progress projects to be a critical component of the 49ers’ ongoing healing process. The team was pleased with how well he covered in the second half at L.A. after some early struggles. Health has proven to be wealth for this defense, which was on a torrid pace before a significant injury rash hit around Week 5.

Pro Football Reference tracks expected points added (EPA) by each phase of the game, and the following per-week breakdown illustrates the 49ers’ precipitous drop-off at the time that they combated their biggest injury issues:

The 49ers’ defense ranked No. 2 by DVOA over the season’s first five weeks. But over Weeks 6 and 7 — those losses to Atlanta and Kansas City — the defense dropped to No. 31. That’s made the 49ers the most volatile defense in the NFL, per DVOA’s variance index.

Were those abysmal performances health-related outliers?

That’s the million-dollar question for the 49ers entering the season’s second half. The final 30 minutes of their win against the Rams were certainly promising. The rest remains to be written, and it starts with a test against the Chargers and their talented quarterback Justin Herbert on Sunday night.

(Photo of Nick Bosa: Ric Tapia / Icon Sportswire via Getty Images)