SANTA CLARA, Calif. -- Let's begin with this: Sam Okuayinonu and Evan Anderson are intriguing, young defensive players who have been far better than anyone expected this season and ought to be part of the San Francisco 49ers' future plans.
The key word in that sentence is "young." These are still-developing linemen who entered the NFL as undrafted rookies. Okuayinonu, 26, began the season with 105 regular-season snaps under his belt. Anderson, 22, is a rookie out of Florida Atlantic who began the season on the practice squad. He's one of the three youngest players on the roster.
These are players you might expect to see in the starting lineup of a mid-August preseason game against the Los Angeles Chargers, not an early-December game against the Buffalo Bills with the playoffs on the line.
And yet there they were Sunday. The 49ers played without three of their top six defensive linemen -- Nick Bosa, Javon Hargrave and Jordan Elliott -- then lost another lineman, Kevin Givens, to a torn pectoral muscle in the first quarter. Add that they were playing on a snow-covered field and it's no wonder the Bills rushed for 220 yards, the second most San Francisco has allowed in the Kyle Shanahan era.
All of which is to say the 49ers don't have a problem with defensive coordinator Nick Sorensen so much as a problem with defensive personnel.
That problem: The personnel is disappearing. At one point Sunday, the defense featured Okuayinonu, Anderson, Kalia Davis and Nick McCloud. Newcomer Khalil Davis had his first significant outing for the 49ers this season, with 18 snaps. So did linebacker Jalen Graham, who was wearing an unfamiliar jersey, No. 41. These days, you have to watch 49ers games with an updated roster in one hand.
Asked how he felt about Sorensen this week, Shanahan didn't hesitate.
"I'm very satisfied with Nick," he said. "I'm not at all satisfied with the results and how it's going right now. But some of the mistakes that we've made ... I don't think it's a schematic issue. It's a little bit more of a fundamental issue. And that also starts with me. That goes to all coaching, and it goes down to the players, it goes to everyone in this building. But the results here these last two weeks haven't changed my opinion on Nick."
It's similar to what Shanahan said in 2018 when fans were calling for then-coordinator Robert Saleh's job.
"We need to improve a lot," Shanahan told The Athletic at the time. "We'll improve our coaching. We'll improve our players. But just because we're facing some adversity, and every time someone misses a tackle or every time there's a busted coverage, that's not a reason for me to think all of a sudden a guy doesn't know what he's doing."
Saleh survived the 2018 season -- with an asterisk. Before the 2019 season, Shanahan hired defensive line coach Kris Kocurek, a specialist in the Wide 9 defensive front. Doing so wasn't exactly a reproach of Saleh. But it was a shake-up for Saleh's system and an indication that Shanahan wasn't satisfied with what he'd been seeing.
The first is that, like any scheme, the Wide 9 the 49ers have been running since 2019 only will thrive with the right personnel, especially at defensive end. Kocurek's arrival that year coincided with the 49ers trading for Dee Ford and drafting Bosa. They joined a group that already included DeForest Buckner, Arik Armstead and D.J. Jones. It's no wonder the Wide 9 got off to such a hot start.
What has the defensive end position looked like this year? Bosa has missed two games -- and counting -- and Yetur Gross-Matos has missed six. Drake Jackson was ruled out for the year before the 49ers were even halfway through training camp. Floyd, one of the NFL's true ironmen, hasn't missed any contests. But he noted Thursday that it took him a few games to get up to full speed.
"At the beginning of the season, it was just me adjusting to the new playing style I had to play," he said. "There's still more to do. I'm trying to get in that playoff mode right now."
The second point is that even if Shanahan thinks Sorensen is doing a fine job, it doesn't mean he won't make a change.
Saleh, fired by the New York Jets on Oct. 8, presumably will be available in the offseason. And it's possible that Jeff Ulbrich, the Jets defensive coordinator who became interim head coach when Saleh left, will be looking for a job as well.
The 49ers were very interested in Ulbrich during the most recent hiring cycle. (The Jets were decidedly less interested in allowing them to interview Ulbrich.) He runs the system Shanahan prefers, is a former 49er and is from the San Jose area. He has the vibrant personality that perhaps the understated Sorensen lacks. Most of all, he's a FOK (friend of Kyle) from their days coaching with the Atlanta Falcons.
And he also might be available. The Jets are 1-6 since Saleh was let go, though Ulbrich's defense ranks third in yards allowed.
What if Shanahan decides to rip up the playbook and go with an entirely different defense as some have suggested? Well, perhaps the hottest defense right now is Vic Fangio's Philadelphia Eagles unit, which leads the league in yards allowed. There's no way Shanahan will be able to pry Fangio, a Pennsylvania native, from the Eagles, but he already has one of Fangio's proteges, Brandon Staley, on his coaching staff.
Shanahan certainly will have options at season's end, though it's hard to fault Sorensen for what's been happening in recent weeks. Saleh, Ulbrich and even Fangio would have a hard time stopping anyone with the group the 49ers have been forced to field.