How will the 49ers' defense change without Javon Hargrave?

SANTA CLARA, Calif. -- After his team coughed up a 14-point lead to fall to the injury-depleted Los Angeles Rams, San Francisco 49ers defensive end Nick Bosa didn't want to move on.

In his postgame interview, Bosa lamented the 49ers' many mistakes and pointed the finger at himself for not doing enough. Then, Bosa and the Niners got the news Monday that defensive tackle Javon Hargrave would likely miss the rest of the season with a torn right triceps.

Even when Bosa showed up to Levi's Stadium for work Wednesday morning, he sat with his fellow defensive linemen for breakfast and couldn't help but miss Hargrave.

"It's been tough to sleep the past couple nights," Bosa said. "I wish I could get it out of my head, but it's frustrating. We're definitely not trying to feel like that anymore."

Whether the 49ers can shed those feelings will depend on how they're able to fill the void Hargrave leaves behind. San Francisco entered this season already without stalwart defensive tackle Arik Armstead, releasing him in a cap-related move after failing to reach agreement on a re-worked contract.

To replace Armstead, the 49ers traded for veteran defensive tackle Maliek Collins. To replace Hargrave, though, the Niners will turn to a combination of Jordan Elliott, Kevin Givens and Yetur Gross-Matos.

None come with the pedigree of Hargrave, a two-time Pro Bowler who was the 49ers' top free-agent addition in 2023 when he signed a four-year, $84 million deal in hopes that he could return their front four to 2019 levels of dominance.

"It hits hard," linebacker Fred Warner said. "Obviously, Javon is a huge part of what we do up front... I feel like he was continuing to ascend, and then he gets injured. So, it's next-man-up mentality. Guys are going to have to step up into that role."

Since coach Kyle Shanahan and general manager John Lynch took over in 2017, they've never shied away from their desire to build a superior defensive line. The idea was to consistently have a front four so difficult to block that blitzes were few and far between.

When Shanahan went in-house with his defensive coordinator hire in the offseason, promoting Nick Sorensen to the role, he acknowledged the need to get back to that basic tenet. That meant again leaning on the front four and tying their pass rush to the coverage.

Schematically, at least, that has been evident through the first three weeks even if the results haven't matched. The Niners are blitzing at the lowest rate in the NFL (14.3%) but have generated just a 26.4% pressure rate, which ranks 23rd, and their pass rush win rate (45%) ranks 12th according to ESPN Analytics.

What success they have had rushing the passer has largely come from Bosa and Hargrave. Bosa (20.4%) and Hargrave (20%) have the two highest pass rush win rates on the team and though Bosa still sees his share of double teams, it's Hargrave who has faced extra blockers the most with a 62.3% double team rate.

When Hargrave has been on the field, the 49ers have a 54.1% pass rush win rate and a 28.8% pressure rate, numbers that drop to 30.4% and 21.9% pressure rate when he hasn't been there.

It's possible Hargrave's absence could mean even more attention is paid to Bosa off the edge, though teams generally use true double teams more often against interior pass rushers. Collins, who is third on the team with a 16.2% pass rush win rate, could also see an uptick in extra blockers without Hargrave around.

That means the 49ers will have to figure out who out of Elliott (who was added to the injury report Thursday), Givens and Gross-Matos might fare the best in one-on-one situations. While Givens has had the longest track record, the answer might be Gross-Matos.

Signed in the offseason in hopes he could fill a similar role to Charles Omenihu or Arden Key where he can play end on run downs and move inside in passing situations, Gross-Matos hasn't had many opportunities inside yet. That's due in part to the 49ers' lack of depth on the edge.

"You've got to make sure you send help, so that leaves opportunities for everybody else," Gross-Matos said. "Everybody else has got to capitalize when one-on-ones present themselves."

One way to help the pass rush would be to create more opportunities by improving against the run. Stuffing the run isn't necessarily a strength of Hargrave's, as opponents are averaging 4.9 yards per carry when he's been on the field and 3.9 when he isn't, though the sample is relatively small.

At 50%, Givens has the best run stop win rate among all 49ers defensive linemen this season, though Elliott's 40% run stop win rate last year ranked seventh among all defensive linemen and sixth among defensive tackles.

Elliott's size (he's listed at 6-foot-4, 303 pounds) makes him an intriguing option to bolster a run defense that is 28th in rush defense EPA (minus-2.26) and success rate against the run (51.6%). Beyond that, the 49ers will also be placing Hargrave on injured reserve, creating a roster spot that will probably be filled by either of two defensive tackles --T.Y. McGill or Evan Anderson-- from the practice squad until Kalia Davis is able to return from injured reserve.

And if the run defense doesn't improve? Well, the 49ers might have to leave their rush four comfort zone and begin dialing up blitzes more frequently. Sunday's game against the New England Patriots(4:05 p.m. ET, Fox) presents a good chance for San Francisco to see whether it has a front capable of taking over a game against a struggling offensive line.

The Patriots are allowing a whopping 46.9% pressure rate, which is 10 points worse than the next closest team and that number only drops to 43.1% when opponents send four or fewer pass rushers. Which should mean the 49ers can stick to their principles for at least another week.

If they can't get after Patriots quarterback Jacoby Brissett without having to blitz, changes might have to follow.

"That's the goal," Shanahan said. "Getting there with four and having seven guys in coverage makes it a lot harder for the offense. But if you can't do that, you've got to mix it up... But it's a huge loss, losing Javon. Guys are going to have to step it up, and when you don't have the rush, then you've got to turn to other things schematically."