49ers’ 2018 ‘Who Is?’ series: San Francisco’s defense
By Peter Panacy

Why the 49ers Defense Regresses in 2018
If there is a major weak spot in San Francisco’s defense, it’s the pass rush.
More on that in a moment, but the Niners still have other question marks hitting home. A year ago, the 49ers cut down on their rush yards against (3.8), which was down a full yard from the atrocious numbers back in 2016.
Despite the improvement, Pro Football Focus still ranked the Niners run defense entering 2018 No. 28 in the league.
Live Feed
FanSided
One can argue whether or not this is an accurate assessment. But with the 49ers facing elite-level runners within the NFC West twice a year (Todd Gurley, David Johnson and promising rookie Rashaad Penny), it will be interesting to see if PFF winds up being right.
As is often the case, depth winds up being a primary defensive concern.
Within the front seven, the 49ers have it. On the back end, though, it’s a bit more problematic. On one hand, defensive back Jimmie Ward has been relegated to backup status after losing his safety job to Adrian Colbert. The good news is Ward has the versatility to play any of the five secondary spots, meaning he’s a prime uber-backup of sorts. Yet his 46.9 overall PFF grade from last year is concerning, as is the fact he’s finished three of his four pro seasons on injured reserve.
Outside of Ward, the Niners secondary lacks experienced depth. Rookies with some pretty hefty expectations include Tarvarius Moore, who is switching from safety to corner, D.J. Reed, Marcell Harris and undrafted free agent Tarvarus McFadden.
Being forced to dip into the depth might be problematic for San Francisco. Especially when one considers how many defensive backs struggle in their transition to the pros.
The Lack of a Pass Rush a Problem?
“It could work,” generally isn’t a great solution to a problem. But that’s the reality of the 49ers’ current situation here.
A year after finishing with just 30 sacks (26th in the NFL), a weak free-agent market and NFL Draft class forced the Niners into relying heavily on 2017 pickup Cassius Marsh and free-agent acquisition Jeremiah Attaochu as primary outside pass-rushers.
On a good note, Marsh generated a pass-rush productivity rating of 9.3 with the Niners last season, per PFF. That would have ranked 22nd out of 39 qualifiers, had he seen enough snap counts, which isn’t terrible.
But the fact both Marsh and Attaochu have a combined 16 sacks over the previous four seasons doesn’t exactly bode well.
Especially if one subscribes to the notion a pass defense is only as good as its pass rush allows it to be.