'Violence is coming': Inside the evolution of Robert Saleh's new-look 49ers defense

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It was déjà vu all over again in the 49ers' locker room.

Marques Sigle flashed a wide grin, raising his right fist to show off a rubber wristband featuring defensive coordinator Robert Saleh's simple mantra: "A.G.N.B."

Though the rookie safety wasn't around back when those bands were the most popular fashion accessory in the 49ers' facility, it's apparent that he understands their significance.

"You better believe that he brought them back," Sigle said before verbalizing the acronym. "All Gas, No Brakes."

During Saleh's first stint as the 49ers' defensive coordinator from 2017 to 2020, he handed those wristbands to anyone who would wear them. They became ubiquitous in the locker room, serving as a constant visual reminder of a fuel that propelled the defense to elite levels. It was Saleh, originally a linebackers coach, who first cultivated the unit-wide pursuit style that bordered on maniacal when the 49ers' defense was at its peak.

Even after Saleh left to be the head coach of the New York Jets in 2021, the wristbands — and defensive success — stuck around. His successor, DeMeco Ryans, oversaw the NFL's No. 2 unit in 2022. Though that defense featured several holdover players from Saleh's first stint, subsequent seasons would feature more roster and coaching turnover (Ryans left to be the head coach of the Houston Texans after that 2022 season) — and the beginning of a painful defensive regression for the 49ers.

By expected points added (EPA), the unit finished No. 10 in 2023 and No. 26 in 2024. Most alarmingly, the 49ers' once-fearsome run defense turned into one of the softest units in the league. They ranked No. 29 in that phase last season. Saleh's wristbands were a relic of the past; brakes were fully engaged, the defense had run out of gas, and the wheels had careened off the wagon.

All of this brought the 49ers back to the very beginning. Coach Kyle Shanahan rehired Saleh, who was fired from the Jets job in 2024, with a familiar goal: Reconstruct the defense just like he did starting back in 2017, when the new 49ers regime inherited perhaps the worst roster in the NFL.

The job isn't as daunting this time around. Saleh's unit features long-tenured stars such as Nick Bosa, Fred Warner, and Deommodore Lenoir. But the 49ers still must replace more than 40% of 2024's defensive snaps, and they're doing so amid an extensive youth movement. The project's first test comes this Sunday, when the 49ers kick off the 2025 season against the Seattle Seahawks.

“We knew what we were getting into," Saleh said with a laugh early in training camp. "But that’s the exciting part, to go do it again. You know, we're going to do it again.”

He's starting by again handing out those familiar wristbands. And young players like Sigle, who projects to start in his very first NFL game, are happy to bring the fashion trend back to the 49ers' locker room.

Nickelback Chase Lucas approached Saleh in the week leading up the 49ers' preseason opener against the Denver Broncos.

"If you let it rip with blitzes," Lucas told his coach, "I'm going to show you some things."

When the game hit, Saleh indeed unleashed Lucas and the 49ers' defense — which started its second-stringers — dominated Denver's first-team offense. Saleh even dialed up pressure that Lucas turned into a safety against Broncos quarterback Bo Nix.

"He stuck true to his word," Lucas said of Saleh in the locker room after the game.

The following week against the Las Vegas Raiders, Saleh did the opposite. He rarely blitzed over the first 59 minutes of the game. But he had Lucas threaten the offensive line anyway. The defensive back repeatedly feigned pressure, and it goaded the Raiders into pointing and barking out his number — "26!" — before numerous snaps. They slid protections in Lucas' direction, which created more favorable matchups for the 49ers' actual pass rushers — and those advantages turned into a handful of pressures and sacks on the afternoon.

Then, with the game on the line in the final minute and the Raiders successfully lulled to sleep by the 49ers' game-long posturing, Lucas actually blitzed. His clutch sack helped set up a dramatic 49ers' victory.

This two-week blend of preseason strategy was significant for many reasons.

For one, it showcased Saleh's ability to maximize talent. Lucas had been with the 49ers in 2024, but then-defensive coordinator Nick Sorensen sported one of the lowest blitz rates in the league. So Lucas, who didn't make the 49ers' 53-man roster and instead spent the entire season on the practice squad, didn't have a proper chance to show off that particular ability.

This year, Lucas is on the 53-man roster — and preseason blitzing was just part of his ticket to make that cut. He also intercepted a pass against the Raiders after Saleh and DB coach Daniel Bullocks had prepared 135 clips of Las Vegas' route-running tendencies — for a preseason game. Based on that tendency tape, Lucas knew that a stutter from the receiver in a 2-by-2 formation against man coverage meant a slant was coming and that no stutter meant an out pattern would instead be on its way.

"I gotta give it to coach Saleh and coach Daniel Bullocks," Lucas said after essentially running an out route for the Raiders receiver to deliver the pick. "I watched their 135 clips of indicator tape probably 10 times. So I read the route perfectly and just broke underneath it."

Lucas' journey to qualifying for the roster further illuminated perhaps the biggest unknown entering Saleh's second term: The how behind the 49ers' defensive approach.

In 2019, Saleh actually recorded one of the lowest blitz rates in the NFL. In 2020, after Bosa tore his ACL, that rate increased — but not dramatically. Saleh's pass-rushing deployment of Lucas and others, including rookie linebacker Nick Martin, during this past preseason suggests the 49ers are willing to gamble much more aggressively to set a tone in 2025.

"It's a tool," Saleh said. "I think in 2019, we could just rush four because we probably had one of the best D-lines in the history of football. But in 2020, we needed to blitz a little bit more. So, you just work off your personnel and what you have."

The 49ers this season will field a young unit that undoubtedly lacks some of the length and experience that Saleh's past defenses enjoyed. But they plan to make up for that with speed, strength, and the spark of youthful exuberance.

And Saleh seems ready to call games accordingly.

It's fitting that Saleh's first game back comes against the Seahawks, considering that the original defense he implemented with the 49ers in 2017 was based closely off the model he learned as a quality control coach in Seattle from 2011 to 2013.

That era featured the rise of the Seahawks' "Legion of Boom", which cemented its status as one of the great defenses in NFL history with a Super Bowl title that closed Saleh's final season in the Pacific Northwest.

When Shanahan hired Saleh to be the 49ers' defensive coordinator in 2017, he tasked his new lieutenant with bringing the Seattle-style defense to the Bay Area. The 49ers took the replication effort so seriously that they signed future Hall of Fame cornerback Richard Sherman, Public Enemy No. 1 to them back when he was with Seattle, to help spearhead the effort.

The start of Sherman's tenure in 2018 intersected with a heavy reliance on Cover-3, a zone defense best operated by tall, physical cornerbacks. Sherman is 6-foot-3 and, not coincidentally, the 49ers sought corners sharing his taller stature at the time.

But starting in 2019, when the 49ers went to their first Super Bowl under Shanahan, Saleh began the aggressive evolution of this defense — a transformation that continued throughout his time with the Jets and has carried over to this 49ers reunion.

“You’re always trying to stay two years ahead of the offense,” Saleh said. “And when we went to the Jets, there were a lot of different things that we started to do. And even now — while we have some things from the Jets — there’s stuff that has evolved over the course of the last four years here, and obviously with the league there’s stuff happening — a lot of really cool concepts, a lot of really cool things.

“Some things are meshed, some things are coming in that are new. A lot of it may seem similar, but there’s a lot of nuance that makes a difference.”

The marked shifts of that 2019 season came both up front — where the 49ers switched to a Wide-9 alignment under new D-line coach Kris Kocurek — and in the secondary, where they introduced a notable shift toward Cover-4 "quarters", a type of zone defense that adopts principles of man coverage (defenders lock onto receivers that enter their zone). Saleh said the 49ers also completely changed their third-down pressure package.

"In '19, there was a major shift in the way we did things," Saleh said. "When we first got here, we installed the Seattle system as I learned it. And then as a staff, evolved. The profile has changed at all three levels."

Throughout the evolution, though, the message on Saleh's wristbands has remained constant: All gas, no brakes. The 49ers continue to search for maniacal movement and violent tackles, even if they no longer prioritize length as much as before.

It's fitting, then, that Sigle and fellow rookie defensive back Upton Stout both project as instant starters in Saleh's 2.0 defense. Along with Martin, they both fit a consistent physical profile: All three of those hard-hitting rookies are smaller than the average player at their respective positions, but simultaneously stronger (Martin and Stout led their position groups with 26 and 21 bench press reps, respectively, at the NFL Combine) and faster (Sigle's 4.37 40-yard dash was fastest amongst all safeties) than their peers.

Length has remained a priority along the defensive line, where the 49ers drafted end Mykel Williams (6-foot-9 wingspan) and tackle Alfred Collins (7-foot-1 wingspan).

This much is clear so far: Saleh is looking for very specific attributes to run the next generation of his defense, and the 49ers — who picked defenders with their top five draft selections for the first time since 1981 — have invested in their returning coordinator's vision.

How exactly Saleh schematically deploys all his new pieces will begin to play out on Sunday. So far, only the highly aggressive tactics of training camp and preseason provide clues.

The 49ers seem confident that this defense, even as it deals with inevitable growing pains, can develop over the coming months into a needed complement to the team's veteran-laden offense.

“From a talent standpoint, Bosa’s here, Fred, [Lenoir], Renardo [Green] — there’s a lot of good talent on this defense,” Saleh said. “So it’s not nearly what 2017 was.”

Said Shanahan last month: "Saleh brought a great deal when he was last here, and I think he's even better now with the experiences he's had. And it's a welcome sight to have him back, the energy that he brings, the expertise that he brings, the leadership he brings.

"I do think people adjust to schemes. You have to adjust, too, depending on your personnel. You have to have the ability, the history and the knowledge of how to change some stuff up when you're in certain situations."

Perhaps star tight end George Kittle, who's watched and practiced against this entire defensive evolution firsthand — he joined the 49ers in 2017, when Saleh came aboard for the first time — can provide the best perspective of what to expect.

"He know what he's talking about," Kittle said this summer of Saleh. "He's inspiring. He gets the boys fired up.

"Violence is coming."