How the defense came crashing down

Last Sunday against the Cardinals, the dam finally broke. The 49ers’ defense, which up to that point had been holding as steady as it possibly could, finally folded. Sure, over the last few games, there were so many pass interference penalties that fans lost count and the occasional missed tackle, but they had also kept the team in games when the offense seemed out of gas and rudderless.

So, what has happened? What’s changed between this year’s iteration from the previous one or, better yet, 2019’s? Obviously, there are surface-level differences, like the turnover of coaching personnel and players, which cannot be overlooked. Robert Saleh’s influence might’ve run deeper than anyone imagined, as a forceful voice in a leadership role that’s been left vacant.

However, by all accounts, DeMeco Ryans hasn’t been terrible. He hasn’t looked over his head during his first brush with defensive play-calling. Besides, there are growing pains for every rookie coordinator. You can ask Saleh about that topic and how he dealt with people wanting him gone until things coalesced in 2019.

There we are back at that year, the Super Bowl appearance that’s one or a couple holding calls away from a Super Bowl victory. It felt like both the culmination of so much team-building yet just the beginning of a new championship window. Now, looking back, I believe what a strength that season has now essentially doomed this one was.

The Shanahan/Lynch philosophy since arriving in the Bay has been fairly straightforward defensively. Amass talent on the defensive line to wreak havoc on opposing quarterbacks, and the rest will take care of itself. This task was made easier by having the duo of DeForest Buckner and Arik Armstead already on the roster from the jump.

Once they traded for Dee Ford and drafted Nick Bosa, plus spent the time finding steals like D.J. Jones or Ronnie Blair, the unit elevated to heights heretofore unseen. The success validated everything; the lost season needed to nab Bosa, the blueprint for an effective defense, and the men attempting to follow said blueprint.

Now, after experiencing the rollercoaster ride of that season would leave a strong impression on anyone. But one thing becomes clear to the coaches and front office: This is the way to construct a roster.

This is the inherent flaw in the 2021 San Francisco 49ers team. Shanahan and Lynch are chasing the ghost of a defensive line that only seemed to exist by a series of small miracles. That’s the problem with nostalgia. You remember the good times, but not all the sacrifices and bumps it took to make those good times possible.

The unraveling started simply enough. Trading away Buckner to stay under the cap and recoup a young player contains the seed of a good idea, but his presence has been sorely missed in the intervening two years. In a circle of life kind of way, it just so happened a ready-made replacement was waiting around that exact spot in the draft, and the team did not hesitate.

Javon Kinlaw, taken 13th overall in the Colts’ slot, flashed early signs of promise and established himself as a valuable cog necessary to stop the run. Yet a wonky knee effectively ended his campaign before it began, and the defense has already suffered tremendously in his absence.

That’s the thing about catching lightning in a bottle. As much as it feels like the math should just add up and everything fall into place, it so rarely does. Take, for example, the other biggest piece from that 2019 run, Richard Sherman. He was two years removed from an Achilles tear, playing on a team-friendly self-negotiated contract, and he performed at an All-Pro level that entire season.

Better still, Sherman’s extensive knowledge of the system made him an invaluable tool to the entire secondary. He could direct traffic on the field as if he were another coach, and his play covered up what was an obvious weak spot.

Having a corner that closes off one side of the field makes it easier for everyone else to defend the other. That’s how you survive an up-and-down Ahkello Weatherspoon and turn to Emmanuel Mosley for stability.

Of course, in moments like these, it’s so hard not to learn the exact wrong lesson, and right now, it’s plain as day that’s what happened here. Shanahan and the front office think it made just as much sense to rely on Jason Verrett to fill that role, and everything else on the other side would work itself out.

Well, we all see how well that turned out, and now the 49ers' thinnest position group has been exposed again and again. It all comes back to trying to recreate that special alchemy that turned 2019 into solid gold—hoping for an oft-injured player to stay healthy and play so well that he hides your biggest deficiency just doesn’t work unless every single piece fits like a puzzle.

Hopefully, even in the broadest sense possible, a new lesson has been learned. Sure, having a mindset on how to build a defense and where to focus resources is one thing, but trying to replicate something so volatile almost always exactly leads to losses. The ability to recognize the difference between the two is how you continue winning.