The 49ers Defense is Struggling Because of its Secondary

Let's take a closer look at the advanced numbers.

The past two weeks, the 49ers defense made Kirk Cousins and Joe Burrow look like prime Peyton Manning and Tom Brady.

What is wrong with the 49ers pass defense? Is it the rush or the coverage?

A quick look at the stats would indicate the pass rush is the problem. The 49ers have 18 sacks this season, which ranks tied for 18th out of 32 teams. Not great, considering the 49ers have Nick Bosa, Javon Hargrave and Arik Armstead -- three extremely expensive pass rushers. And yet, no one on the defense has more than three sacks.

But the pass rush isn't the issue.

Let's take a closer look at the advanced numbers. According to Pro Football Reference, the 49ers defense generates pressure 25 percent of the time when the opposing quarterback drops back to pass -- 9th best in the NFL. Last season, the 49ers defense generated pressure 22.9 percent of the time -- 11th best in the NFL. So the pass rush actually has improved since last season, which is to be expected with the addition of Hargrave.

So why haven't sacks gone up?

Because the secondary has gotten worse, and new defensive coordinator Steve Wilks doesn't seem to trust the corners, which is understandable. Charvarius Ward is a penalty waiting to happen, and Deommodore Lenoir and Isaiah Oliver both are liabilities. So Wilks calls lots of soft zone coverage to protect his subpar cornerbacks, which doesn't give the pass rushers enough time to sack the quarterback, because he can make quick easy throws.

If the 49ers trade for a legit cornerback today before the deadline, their pass rush will come back to life. If they trade for another defensive lineman, their secondary will continue to short circuit the pass rush.

Let's see what the 49ers decide to do.