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Why the 49ers' defense suddenly is so concerning

Originally posted on San Francisco 49ers on SI
By Parker Hurley | Last updated Dec 23, 2025 3:00 PM ET

The San Francisco 49ers offense was unstoppable against the Indianapolis Colts in Week 16. Brock Purdy was a playmaker, and the run game looked better than ever.

However, as exciting as the offense was, the defense brought just as many questions.

How concerning is the San Francisco 49ers defense?

The 49ers allowed 27 points on defense. They did record a pick-six at the very end to put the game away, but the Colts were driving before that happened. Had the 49ers not recovered a fumble from their special teams, they would have needed to score on every drive just to have a lead on the Colts.

Philip Rivers was excellent against the 49ers. He was decisive and accurate. However, he was just retired a few weeks before and clearly did not have the physical ability to drive the ball in certain spots. Beyond that, the Colts were missing their two starting tackles. They lost five of their last six games coming into the game and they were not an offense that people were fearing.

Even on the 49ers' end, they got Tatum Bethune, Eric Kendricks, Yetur Gross-Matos, and Sam Okuayinonu healthy and into the lineup. Those are notable upgrades.

It did not help that the team had to start Darell Luter at cornerback. He was getting beaten often. Still, even Deommodore Lenoir and Upton Stout struggled. Both safeties had issues with the scheme that the Colts ran, and the upgrade at linebacker did not make enough of a difference.

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However, the 49ers' defense had legitimate struggles defending them.

This has to be concerning. The Colts offense would be the worst offense that the 49ers will face moving forward. There is a real chance the 49ers are going to be allowing 30 points per game the rest of the season.

The offense is excellent, but it is asking a lot for them to continue to play like this and win shootouts. It is one thing to do it against the Colts and Tennessee Titans; it may not be quite as easy to put up 40 points on the Seattle Seahawks.

This game showed just how the 49ers can win in the playoffs, and that is by scoring 40 points. However, it also showed how they would likely get eliminated if that were to happen. If the offense faces better quarterbacks than Rivers and the offense cannot outscore them, can the defense make enough stops to take the offense seriously?

This article first appeared on San Francisco 49ers on SI and was syndicated with permission.

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