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Could the Bears Switch Back to a 4-3 Defense?

With some of the latest Defensive Coordinator interviews, it’s worth exploring whether the Bears could be considering a change to a base 4-3 defense.

Bears vs. Jaguars Nuccio DiNuzzo/Chicago Tribune/MCT via Getty Images

When Marc Trestman and his staff were shown the door at the end of the 2014 NFL season, the Bears knew they needed to make big changes on the defensive front. Brian Urlacher had retired a few years prior, and the team didn’t view Lance Briggs as healthy enough for another contract. Without elite linebacker play, they couldn’t justify a base 4-3 scheme any longer and hired defensive head coach John Fox to stabilize the organization. To lead Fox’s defensive staff, the Bears brought veteran coordinator Vic Fangio along to spearhead the effort to switch their terminology and base packages to 3-4.

For an organization which had been predominantly a 40 front defense in basically forever, this was a huge change.

Since that change in 2015, the Bears defense grew steadily better every year under Fangio’s 3-4 scheme. In 2017, they moved into the top-10 in points allowed per game, a tier in which they remained for 3 consecutive years. That included a year (2019) without Fangio, who had left to become head coach of the Broncos. The Bears defense has since been headed by former Indianapolis Colts head coach Chuck Pagano. After a slight decline in defensive production in 2020, Pagano retired and current head coach Matt Nagy was left to search for his 3rd defensive coordinator in 4 years.

One of the more interesting interviews the Bears have conducted during their defensive coordinator search is George Edwards, who previously held the position for the division-rival Vikings from 2014-2019. During his time in Minnesota, Edwards employed a 4-3 system which had it’s share of playmakers who could take games over. The Bears have also interviewed Jonathan Gannon and Mike Singletary for the defensive coordinator position, who both have careers in base 4-3 schemes. It’s fair to wonder: how would a switch to a base 4-3 defense affect the Bears personnel?

Brad Biggs, a beat writer for the Chicago Tribune, did an excellent job answering this question in his most recent weekly Q&A. When asked if he thought the Bears could switch to a 4-3 defense this offseason, he wrote:

The Bears would need to add linebackers in a 4-3 scheme too — one if they keep Danny Trevathan and two if they part with him. Keep in mind they need to re-sign strong safety Tashaun Gipson or add a new safety as well. With all of the issues the Bears have on offense, I don’t think it’s a good idea to create more change on defense than is necessary. They can play a 30 front, a 50 front (which they used a lot this season) and a nickel front, but I’m not sure converting to a 40 front for their base defense is the best use of their current personnel.

It’s worth mentioning that most NFL teams play sub packages outside of their base around 60% of the time, and the Bears are no exception. Personnel will always be determined by matchups, and the main difference between 3-4 and 4-3 is terminology, not snap counts. With the success the Bears have had in 3-4 defense, though, and the chance that the defense will again have to lead the effort for the Bears, it’s unlikely the team will make a major change to their defensive playbook. The incoming defensive coordinator will more likely have to gear his terminology around what the players are more comfortable with as a unit.

That said, if the Bears switched to a 4-3 defense, what players would see the greatest change?

(For those looking for an excellent course through defensive position terms, check out Matt Bowen’s article for Bleacher Report)

Khalil Mack:

Indianapolis Colts v Chicago Bears Photo by Jonathan Daniel/Getty Images

3-4 position: Outside Linebacker

4:3 position: Closed Defensive End

This is a minor change, as Khalil Mack often lines up against a right tackle and rushes the edge. That wouldn’t change in a base 4-3 defense. When getting creative, the Bears sometimes drop Mack into pass coverage, and a big change would be Mack dropping into the inside gaps to cover run plays on creative sets. In either case it’s a rare occurance for Mack to be doing anything other than chasing quarterbacks, so this shouldn’t concern Bears fans as a scheme change.

Robert Quinn:

New Orleans Saints v Chicago Bears Photo by Jonathan Daniel/Getty Images

3-4 Position: Outside Linebacker

4-3 Position: Open Defensive End

The Bears struggled to “unlock” Robert Quinn in 2020, and he finished the years with just 20 total tackles and 2 sacks. There was a bit made of Quinn’s adjustment to a 3-4 scheme when he signed with the Bears last offseason, after he had previously referred to the scheme as “suffocating.” He’s played some of his best football in base 4-3 defenses, and it offers a player of his skillset freedom to move around to play to his strengths. Quinn could sub into packages as a standup linebacker and still rush B gaps, and the change is significant enough that it may be what the Bears need to get the production from Quinn to match his $14.7 million cap hit.

Roquan Smith:

NFL: Chicago Bears at Los Angeles Rams Robert Hanashiro-USA TODAY Sports

3-4 Position: Inside Linebacker

4-3 Position: Weak Side (Will) Linebacker

Roquan is a player who was drafted #8 overall for a reason. As far as football instincts go, you’ll be hard-pressed to find someone better who’s not currently in, or otherwise destined for Canton. He could truly play any of the three linebacker positions in a base 4-3 system, but the Bears have been moving him around so often lately, between covering receivers to protecting against outside runs to blowing up the pocket. To efficiently play Smith in a 4-3 system, a coach would have to look at which position requires the most versatility, and they would almost certainly land on the Will Linebacker. Put the Bears leader in tackles at a position where he’s chasing the football every snap, and offensive coordinators start questioning play calls.

Danny Trevathan:

NFL: Chicago Bears at Minnesota Vikings Brad Rempel-USA TODAY Sports

3-4 Position: Inside Linebacker

4-3 Position: Middle (Mike) Linebacker

The Bears are locked into at least 1, but likely 2 more years of Danny Trevathan, who’s on the wrong side of 30 and becoming limited in his abilities. The Bears need to keep Trevathan in the box, and covering inside runs, which is exactly what the Mike Linebacker is tasked with in a 4-3 defense. The Bears can’t afford to have Trevathan in pass coverage downfield, so they need him in the middle for Cover-1 and watching running backs otherwise.

For those keeping score, this leaves a sizeable hole in the defensive personnel, the Strong Side (Sam) Linebacker. Hicks and Goldman would seamlessly fill the two defensive tackle positions, but to truly convert to 4-3 it would require somebody playing out of position, or else it would require a free agent signing at the Sam position to round out the personnel.

One notable free agent this offseason for a 4-3 strong side linebacker will be Justin March-Lillard, who has most recently played 3 seasons for the Cowboys. The Bears interviewed George Edwards, who spent last season as a senior defensive assistant for the Cowboys, for their vacant defensive coordinator position. If Edwards is hired, and the Bears make the switch to 4-3, look for March-Lillard to be a target in free agency.