There has been a lot of discussion over the past few weeks about the changes coming to the San Francisco 49ers’ defense in 2019. Much of this talk has come from interviews with coaches and players during the Niners’ recent minicamps and offseason workouts. Let’s break down what we’ve heard and the effects these changes will have on the 49ers’ defense for the upcoming season.

49ers Defense: Wide-9 Technique

The first major defensive change comes from the 49ers’ new defensive line coach, Kris Kocurek. Kocurek, who previously worked in the same capacity for the Miami Dolphins and the Detroit Lions, brings an emphasis on the “wide-9 technique.” The wide-9 technique refers to the alignment of the defensive end, who lines up in the D gap outside the tight end, regardless of whether the offense has a tight end on the field. Kocurek prefers this technique because it enables the pass rusher to have a better angle to attack the quarterback. Here’s an example of how the 49ers used the wide-9 technique last year with their nickel personnel:

In the example above, the Tampa Bay Buccaneers are in an obvious third-and-long passing situation. Having both defensive ends line up outside of the offensive formation leaves the defense susceptible to inside runs, so this type of look should be used exclusively in passing situations. Last month, when 49ers defensive coordinator Robert Saleh discussed the use of the new wide-9 alignment, he broke down an example alignment for the defensive line. According to Saleh, the defensive linemen will be lined up in 9-technique, 0-shade, 3-technique, and 5-technique. The image below shows the Dolphins — under Kourick — in a fairly similar defensive formation:

49ers Defense: Stacked Linebackers

The second change that has been discussed over recent weeks is the modified role of the SAM linebacker. Instead of lining up on the line of scrimmage, the SAM linebacker will be stacked next to the MIKE and WILL linebacker, similar to the linebacker alignment in a traditional 4-3 over. Saleh used the SAM linebacker on the line of scrimmage to both set the edge on runs and attack the quarterback on blitzes. Here is an example from last year, with Mark Nzeocha playing the SAM linebacker position. With Nzeocha on the line of scrimmage, strong safety Marcell Harris moves down into the box to help fill the void left by the SAM:

Given the proposed changes for 2019, the 49ers will no longer need a big-bodied SAM linebacker responsible for setting the edge. The 49ers have linebacker Fred Warner at MIKE and newcomer Kwon Alexander at WILL, but the third linebacker position is up for grabs. When the 2019 season begins, linebackers Elijah Lee, Malcolm Smith or Dre Greenlaw could get the starting nod. The 49ers used a three-linebacker stack on occasion in 2018, including during their December matchup against the Seattle Seahawks:

49ers Defense: Interchangeable Safeties

The third planned change for the 49ers’ defense pertains to the positioning and responsibilities of the team’s two safeties. In 2018, the 49ers primarily used a single-high safety to cover the deep third, while lining up a strong safety in the box. Below, the 49ers are lined up with nickel personnel against 11 personnel in their opening game against the Minnesota Vikings. Strong safety Jacquiski Tartt is stacked next to the WILL and MIKE linebackers and free safety Adrian Colbert is playing 15 yards off the line of scrimmage:

During OTA’s, players and coaches told reporters the team’s safeties will be more interchangeable in 2019. Planned changes include the option for San Francisco’s free safety to line up in the box to help defend against the run while the strong safety mans the deep middle. Colbert has bulked up over the offseason — adding an additional 10 to 15 pounds — in order to prepare for the rigors of playing closer to the line of scrimmage. Tartt has the versatility to play the deep third and has experience playing free safety for the 49ers in the past. At times under Saleh, the 49ers used this type of safety switch, as seen in the image below, with Colbert close to the line of scrimmage, and Tartt lined up deep in the middle of the field:

The 49ers’ front seven are expected to take a significant step forward this season due to the additions of edge rushers Nick Bosa and Dee Ford, as well as Alexander. The added talent coupled with the planned schematic changes could have the 49ers’ defense primed for a breakout year in 2019.

However, questions remain regarding the state of San Francisco’s secondary, which has major room to improve after a 2018 season resulting in just two interceptions and a pass defense that ranked 27th in DVOA, per Football Outsiders. At cornerback, the 49ers need Ahkello Witherspoon to return to his 2017 form and free-agent-acquisition Jason Verrett to stay healthy. At safety, the Niners need Colbert to improve significantly after a down year in 2018 and Jimmie Ward to get and remain healthy. The 2019 San Francisco 49ers’ defense comes with a lot of question marks, but also a lot of potential. Either way, we’re looking forward to seeing how it all plays out once the season begins.

Follow Aaron Wilson on Twitter at @aaronwilson22