San Francisco 49ers: Breaking down defensive line’s alignment in 2017

October 22, 2015; Santa Clara, CA, USA; General view of the line of scrimmage between the San Francisco 49ers and the Seattle Seahawks during the first quarter at Levi's Stadium. Mandatory Credit: Kyle Terada-USA TODAY Sports
October 22, 2015; Santa Clara, CA, USA; General view of the line of scrimmage between the San Francisco 49ers and the Seattle Seahawks during the first quarter at Levi's Stadium. Mandatory Credit: Kyle Terada-USA TODAY Sports /
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Oct 16, 2016; Orchard Park, NY, USA; San Francisco 49ers defensive end Arik Armstead (91) against the Buffalo Bills at New Era Field. Mandatory Credit: Timothy T. Ludwig-USA TODAY Sports
Oct 16, 2016; Orchard Park, NY, USA; San Francisco 49ers defensive end Arik Armstead (91) against the Buffalo Bills at New Era Field. Mandatory Credit: Timothy T. Ludwig-USA TODAY Sports /

The San Francisco 49ers will employ a 4-3 under base defense in 2017, which means there’s some tweaking to be made to the personnel in place. Niner Noise breaks down the alignment and predicts the depth chart this season.

One of the major changes the San Francisco 49ers will implement this season is a shift from a 3-4 to a 4-3 base scheme.

Defensive coordinator Robert Saleh, a pupil of former Seattle Seahawks defensive coordinator and Jacksonville Jaguars head coach Gus Bradley, is looking to copy the same sort of 4-3 hybrid the Seahawks have ran, defensively, the past few seasons.

This type of scheme calls for a 4-3 look but employing 3-4 personnel. It’s not new to the NFL, but it’s something the Niners figure will best utilize the available personnel on the roster.

San Francisco 49ers
San Francisco 49ers /

San Francisco 49ers

San Francisco has invested heavily in its defensive line the past few seasons. In 2015, the 49ers brought in defensive end Arik Armstead in Round 1 of the NFL Draft. This pick was followed up with fellow D-linemen DeForest Buckner in 2016 and Solomon Thomas this season.

Additionally, the Niners brought in free-agent nose tackle Earl Mitchell and selected rookie D.J. Jones late in the draft this year.

These players, along with other incumbents on the roster, comprise a unit going through a number of notable changes this offseason.

Niner Noise takes an all-encompassing look at how each alignment will work this upcoming season — in both base and nickel packages — and what the depth chart might look like by the time Week 1 rolls around.

Let’s kick things off with the base defense.