49ers 2018 offseason positional preview: Defensive line

MINNEAPOLIS, MN - SEPTEMBER 23: The defense for the San Francisco 49ers lines up against the offense of the Minnesota Vikings during the third quarter on September 23, 2012 at Mall of America Field at the Hubert H. Humphrey Metrodome in Minneapolis, Minnesota. The Vikings defeated the 49ers 24-13. (Photo by Hannah Foslien/Getty Images)
MINNEAPOLIS, MN - SEPTEMBER 23: The defense for the San Francisco 49ers lines up against the offense of the Minnesota Vikings during the third quarter on September 23, 2012 at Mall of America Field at the Hubert H. Humphrey Metrodome in Minneapolis, Minnesota. The Vikings defeated the 49ers 24-13. (Photo by Hannah Foslien/Getty Images) /
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GLENDALE, AZ – OCTOBER 01: Defensive tackle DeForest Buckner #99 and defensive end Arik Armstead #91 of the San Francisco 49ers react after a defensive stop during the second half of the NFL game against the Arizona Cardinals at the University of Phoenix Stadium on October 1, 2017 in Glendale, Arizona. (Photo by Christian Petersen/Getty Images)
GLENDALE, AZ – OCTOBER 01: Defensive tackle DeForest Buckner #99 and defensive end Arik Armstead #91 of the San Francisco 49ers react after a defensive stop during the second half of the NFL game against the Arizona Cardinals at the University of Phoenix Stadium on October 1, 2017 in Glendale, Arizona. (Photo by Christian Petersen/Getty Images) /

The San Francisco 49ers have invested heavily in their defensive line the past few years. And while it’s deep, questions remain, and we break those down in this 2018 preview.

Fortunately, the San Francisco 49ers boast one of the best up-and-coming defensive linemen in the NFL right now, third-year pro DeForest Buckner.

Buckner is just one of the numerous high-profile investments the team has made over the past few years, starting notably back in 2015 when former Niners general manager Trent Baalke grabbed defensive tackle Arik Armstead in Round 1 of that year’s NFL Draft.

Switching to a 4-3 Under base a year ago, this unit has gone through a bit of reshuffling but still retains some serious talent.

But despite the investments and attention, there are some notable questions as the 49ers gear up for their 2018 campaign.

Most crucially, the pass rush.

A year ago, San Francisco finished tied for 26th with just 30 sacks. The Niners’ leading sack specialist, EDGE Elvis Dumervil, is no longer with the squad, mostly leaving the outside pass-rushing duties to unproven and less-known players.

It’s a formula that could come back to haunt the 49ers this season. Yet with relatively few options in free agency and this year’s draft to address it, it’s likely current GM John Lynch merely wanted to table the need for another time.

With training camp set to start on July 25, though, what’s in the plans for this crucial in-the-trenches unit heading forward?

Niner Noise breaks down the D-line in this comprehensive 2018 preview.