Why the 49ers are struggling defensively without Arik Armstead

Is it possible for one player to make as much of a difference as Arik Armstead has made for the 49ers? On the surface, you look at Armstead’s stats, and he has a tackle for loss, one run stop, no sacks or QB hits, and one pressure on the season.

The 49ers defensive DVOA in Week’s Armstead played: -10.2%.
In the four games, Armstead didn’t play: 9%

That’s a drastic difference. And nobody will argue Armstead was the reason the 49ers fell to the Chiefs Sunday. Still, over the last two seasons, Armstead has been a top-three run defender in the NFL — especially since his full-time move to defensive tackle.

The Chiefs' rushing DVOA was a whopping 51.9% in Week 7. That was the highest number the 49ers' defense has allowed since Week 1 in 2019. We’ll find out Wednesday whether or not Armstead practices. San Francisco needs Armstead against the Rams. Unfortunately, he didn’t practice on Wednesday.

During today’s episode of The Shanaplan, we discussed the importance of Armstead and how surprising it was to see the coaching staff outcoached two weeks in a row:

“I think the biggest surprise was seeing the coaches get completely taken to school by opposing coaches two weeks in a row. It felt like Arthur Smith was all over DeMeco Ryans last week. Controlled the game flow. Basically, had control of that entire game.

The Chiefs went down 10-0, but it never felt like they were out of it. They flipped the switch. The 49ers had no answer. So seeing Kyle Shanahan and DeMeco Ryans get outcoached two weeks in a row. And now they get Sean McVay off a bye. So they’ve had an extra week to prepare. So that gives me a little bit of a pause this week.”

History is on the 49ers' side. San Francisco is favored despite losing two games in a row, and their opponent coming off a bye would suggest they’re the better team in Week 8. The same rings true for the matchup and when you compare the Niners and Rams statistically.

As always, it’ll come down to whether the offense can stop shooting themselves in the foot in opponents’ territory and if the defense can revert to the same unit we saw during the first month of the season.