Why the San Francisco 49ers Should Switch To A 4-3 Defense

Since the arrival of Jim Harbaugh and Vic Fangio, the San Francisco 49ers have consistently been among the elite defenses in the entire National Football League. Spearheaded by a philosophy predicated on eliminating the opponent’s rushing attack, Fangio has been able to build arguably the most dominant front seven of the best four seasons.

The success of the 49er run defense originates from Fangio’s unique implementation of the 3-4 defensive front. While most modern defenses have steered towards the 4-3 defensive front due to the greater athleticism found in today’s defensive linemen, the Niners have found great success with their base 3-4 alignment, consisting of three linemen and four linebackers. While they tend to display hybrid fronts on later downs, the most prominent base defense the 49ers have shown throughout the Jim Harbaugh era has been the 3-4 front.

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The success of the 3-4 front in San Francisco is largely attributed to the extraordinary talent the Niners have possessed at the linebacker positions for the last few years and the underrated abilities of defensive tackles Justin Smith and Ray McDonald. The inside linebacker duo of Patrick Willis and NaVorro Bowman has been far and away the best in the league in stuffing the run, rushing the passer, and, perhaps most importantly, covering tight ends and running backs on passing downs.

The outside linebacker tandem of Aldon Smith and Ahmad Brooks is equally dominant, as both Smith and Brooks have proven to be ferocious pass rushers off the edge in addition to setting the edge against the run. And of course, the stellar play of the linebackers is due to the impact tackles Justin Smith and McDonald have in holding offensive linemen up at the point of attack.

Despite everything the 49ers have achieved over the last four seasons behind this 3-4 front, it may finally be time for Fangio to consider making the difficult decision of transitioning into a base 4-3 front. In fact, the 49ers already use a 4-2 front when they bring in their nickel defense, a defense that the Niners put on the field 60 percent of the time.

On passing downs or when opponents utilize three-receiver sets, the nose tackle playing in the base 3-4 alignment (currently Ian Williams, Glenn Dorsey, and Quinton Dial) comes out, the nickel cornerback comes in (Dontae Johnson, Perrish Cox, and Jimmie Ward), and the outside linebackers (Aldon Smith, Brooks, and Aaron Lynch) move to the defensive end spots. So, as it stands now, the 49ers already play more four-linemen fronts than three-linemen fronts.

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However, in light of the changing personnel in the front seven this season and beyond, Harbaugh and Fangio should highly consider making a more permanent shift to a base 4-3 front. With the absences of the Niners’ superstar middle ‘backers in Willis and Bowman, rookie Chris Borland has truly shined as a playmaker in the middle of the defense. While he has made some rookie mistakes, notably a few blown coverages, it has been abundantly clear that Borland is far too talented to bench upon the return of Willis and Bowman. If the 49ers make the switch to a 4-3 defense, all three can stay on the field without their roles being altered drastically.

Additionally, a switch to the 4-3 front could help to stimulate the Niners’ anemic pass rush. The return of sack artist Aldon Smith should generate greater pressure on opposing quarterbacks for the rest of this season, but shifting Smith from a 3-4 outside linebacker to a 4-3 defensive end could prove to be a necessity by the end of this season. The engine that makes the 49ers’ defense run during their run of dominance has been defensive tackle Justin Smith, and while Justin Smith has had an incredible career in San Francisco, his tenure in the red and gold is inevitably drawing to a close.

When the lifeblood of their defensive line is gone, the 49ers would do well to usher in a new era of Niner defense by using Dorsey and Williams as gap-penetrating interior linemen and Aldon Smith and Lynch as 4-3 edge-rushing defensive ends. All four are highly capable run defenders as well, so the 49ers would likely not lose production in that department. The roles of Bowman and Willis would not change much either, as they would essentially be performing the same duties as a 3-4 middle linebacker while playing 4-3 outside linebacker.

Fangio has been a master at manipulating personnel and getting the best product out of the players on the field. With the looming departure of the Cowboy and Borland’s emergence, he would be wise to consider a permanent shift to an attacking 4-3 defense.