How the 49ers Defense will Evolve under Robert Saleh in 2025

Let's focus on their defensive line.

Sep 9, 2024; Santa Clara, California, USA; New York Jets head coach Robert Saleh (right) talks with San Francisco 49ers head coach Kyle Shanahan (left) before the game at Levi's Stadium. Mandatory Credit: Darren Yamashita-Imagn Images | Darren Yamashita-Imagn Images

The 49ers defense hasn't changed much schematically since Robert Saleh left in 2021.

But the league has evolved, and so has Saleh, who's the 49ers defensive coordinator now for the second time, which means their defense could look much different this year than it did in 2024.

Let's focus on their defensive line. In 2019, the 49ers hired defensive line coach Kris Kocurek and installed his Wide 9 defense. They did this primarily to stop the Los Angeles Rams who were the team to beat at the time considering they had just gone to the Super Bowl.

Back then, the Rams primarily used three-wide receiver formations and were a much bigger threat to run outside the tackles than between them. So the 49ers wanted to set edges in the run game, which the Wide 9 allowed them to do.

Now, the Rams and most NFL offenses primarily use two tight end formations which can easily exploit a Wide 9 front. The extra tight ends make the gaps between the defensive linemen even larger than normal and the defense becomes extremely susceptible to runs up the middle.

There's no good reason to use a Wide 9 front against a team such as the Eagles, the Ravens or the Lions -- teams that are committed to running the ball out of heavy formations. And now, the 49ers don't have to.

Their first-round pick this year, Mykel Williams, played both defensive end and defensive tackle at the University of Georgia. He gives the 49ers the versatility to play a five-man front against the best rushing teams because he can move inside.

I'm confident that's a big reason the 49ers drafted him.