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49ers' rookie defensive linemen face a steep learning curve as they aim for an NFL impact

SANTA CLARA, Calif. (AP) — Few teams have the star power of the San Francisco 49ers, who feature several of the top players in the game, including Trent Williams, Nick Bosa, Fred Warner and Christian McCaffrey.
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San Francisco 49ers defensive end Mykel Williams waits for his turn to run a drill during practice at the team's NFL football training camp, Thursday, July 31, 2025, in Santa Clara, Calif. (AP Photo/Godofredo A. Vásquez)

SANTA CLARA, Calif. (AP) — Few teams have the star power of the San Francisco 49ers, who feature several of the top players in the game, including Trent Williams, Nick Bosa, Fred Warner and Christian McCaffrey.

San Francisco's hopes for a major turnaround following an injury-plagued six-win season might depend on a bunch of untested players on the defensive line.

The Niners used three of their top five picks on defensive linemen and will need major contributions from those rookies if they want to get back to the postseason. The early results show signs of promise, but the 49ers know that counting on rookies to make an immediate impact can be a dicey proposition.

“We may not know who they are until the midway point of the season. They’re rookies,” defensive coordinator Robert Saleh said. “As soon as we hit Week 1, it’s going to start all over. They’re going to be leaning on new bodies, new blocking schemes, and they’ve got to learn week to week what they’re putting on tape and understand that part of the game that’s happening in there. Right now, you just want to see those guys play as hard as they can, as violent as they can and you trust that as they get more reps, they’ll learn how to play the game a little bit better and get better every day.”

The results from the new-look defensive line were mixed in the preseason opener against Denver, but the group gets another chance this week with a joint practice against the Las Vegas Raiders on Thursday and an exhibition game Saturday.

Defensive line coach Kris Kocurek has been pleased with the progress so far from rookies Mykel Williams, Alfred Collins, C.J. West and Sebastian Valdez but knows there's a lot more work to do.

“It’s a learning curve, especially coming from the way colleges are kind of constructed and offenses that they see in college compared to jumping into the NFL,” Kocurek said. “It’s even a stronger learning curve than probably it was seven, eight, nine years ago when colleges ran the ball more. Now it’s a lot of the pass game, RPO, up-tempo stuff. So for D-lineman coming from college to the NFL, there’s a learning curve that’s involved in there and it’s getting steeper it seems like every year.”

The 49ers are counting most on Williams, who was drafted 11th overall. He has shown flashes in practice of being the run-stopping defensive end they need but also has dealt with a series of minor injuries, including a hyperextended knee that will prevent him from playing until at least the preseason finale next week.

Collins, the second-round pick, missed the offseason program while recovering from a calf injury and is still getting up to speed.

“He was way far behind the eight ball, and I felt like this past weekend, especially in the game, he took a really, really good step in terms of strain and power at the point of attack,” Saleh said. “I think the next step for him is to get off blocks, play with great pad level, go make some plays.”

The less-heralded players have fared better.

West, picked in the fourth round, has flashed repeatedly in practice with his strong hands, and Valdez, an undrafted rookie out of Washington, has been able to get consistent penetration and is making a serious bid for the roster.

West's power showed up at times against the Broncos, but he also got pushed around on other plays.

“At this level, offensive linemen are smarter, they’re faster, and they know different ways to bend the rules just a little to give themselves an advantage,” he said. "(It) was definitely humbling, going up against the starting offensive line and this other team. There’s a lot to learn in order to get better.”

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AP NFL: https://apnews.com/NFL

Josh Dubow, The Associated Press