One Area That is Becoming a Weakness for the 49ers

The 49ers better get this area back up to speed, or they will struggle in the coming games.

Dec 14, 2025; Santa Clara, California, USA; Tennessee Titans running back Tony Pollard (20) runs with the ball during the second quarter against the San Francisco 49ers at Levi's Stadium. Mandatory Credit: Cary Edmondson-Imagn Images | Cary Edmondson-Imagn Images

It’s been nothing short of incredibly impressive for the San Francisco 49ers to be 10-4.

With so many injuries to star and key players, they should’ve been sunk a long time ago. The 49ers don’t even have an effective pass rush. Yet, they’re getting by just fine.

However, it’s becoming difficult for the 49ers to simply get by. That is due to one area starting to steadily decline into a new weakness on the team.

The 49ers have to stop this decline

Oct 19, 2025; Santa Clara, California, USA; San Francisco 49ers defensive coordinator Robert Saleh congratulates San Francisco 49ers linebacker Dee Winters (53) during the second quarter against the Atlanta Falcons at Levi's Stadium. Mandatory Credit: Darren Yamashita-Imagn Images | Darren Yamashita-Imagn Images

It’s with their run defense. This area played a key role in the Titans making a run in the second half of the game. Now, as it stands, the 49ers still have some decent rankings against the run.

They are the No. 12-ranked defense in yards per game allowed (106.1) and the No. 15-ranked defense in team run stuff rate (16 percent).

However, their run defense has been leaky. Tony Pollard just gashed them for 104 yards on 14 carries. That’s a whopping 7.4 yards per carry. Two games before that, against Carolina, the 49ers let Rico Dowdle be effective.

He ran for 6.3 yards per carry. The only reason Dowdle wasn’t a significant factor in that game was that the Panthers were pass-happy for whatever reason. The 49ers were fortunate for that.

Of course, there were a couple of solid defensive performances against the run. But one was against the Cardinals, who the 49ers got out to an early lead and rendered the run useless. 

Another was against the Browns, where the 49ers sold out for the run to force Shedeur Sanders to beat them. When the 49ers have to face fierce rushing attacks, they will get gashed.

Sep 14, 2025; New Orleans, Louisiana, USA; San Francisco 49ers defensive end Mykel Williams (98) tackles New Orleans Saints running back Alvin Kamara (41) during the second half at Caesars Superdome. Mandatory Credit: Stephen Lew-Imagn Images | Stephen Lew-Imagn Images

That’s what happened against the Rams in Week 10 when they allowed 126 yards. One significant factor that is negatively impacting the 49ers' run defense is Mykel Williams’ absence.

With Williams on the field, the 49ers allowed 3.99 yards per carry and a  45.2 percent rush success rate. Without him, they are allowing 4.58 yards per carry and a 51.3 percent rush success rate.

The 49ers drafted Williams to improve their run defense. He succeeded in accomplishing that before tearing his ACL in Week 9. Losing him has stung the 49ers, and maybe even Tatum Bethune.

Curtis Robinson isn’t a sound run defender, and it shows with Bethune out. Getting healthy players should help reinforce it. Nevertheless, Robert Saleh has a tall task ahead of him.

The teams they will face in the playoffs will make note of how to attack the 49ers. It’s already bad enough that they have a nonexistent pass rush. 

If their run defense continues to slide, they will stand no chance in the playoffs.

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