SANTA CLARA, Calif. (AP) — The San Francisco 49ers turned to a familiar old face in coordinator Robert Saleh to help fix a defense that uncharacteristically struggled last season.

The success of that unit in 2025 might depend heavily on the contributions from a group of rookies that is being counted on to contribute right away.

That group led by first-round defensive end Mykel Williams has already changed the environment around the 49ers following last season’s six-win season and will get its first action in the season opener Sunday at Seattle.

“The energy is different, just the youth,” star defensive end Nick Bosa said Wednesday. “The energy on the field and off the field. It’s kind of refreshing. They’re all coming along and getting better.”

The Seahawks offer a tough test with a new-look offense under first-year coordinator Klint Kubiak that is expected to feature extensive use of misdirection, play action and motion in a run-heavy scheme.

It’s a similar offense to the one the Niners saw all of training camp during practice but can be confusing, especially for rookies.

“It’s a real challenge,” star linebacker Fred Warner said. “Not just for young guys, but for old guys, too. You got to remember the situation that you’re in, not making it bigger than it needs to be.”

After not playing a single rookie for any defensive snap in the season opener the past two seasons, the Niners could have several hit the field Sunday. Williams is set to start at defensive end and could see time inside as a pass rusher after being drafted 11th overall.

Williams missed significant time in training camp with various minor injuries and didn’t play in any exhibition games but has impressed the 49ers already.

“I’m really interested to see if his production matches up to that promise, because the faith that he’s instilled in this locker room and how we think he will play,” star left tackle Trent Williams said. “I think it’s kind of a consensus. I’m just hoping and praying it works out the way everybody hopes.”

Fifth-round safety Marques Sigle has a good chance to start and third-rounder Upton Stout will be the team’s top nickel back and should see plenty of snaps when Seattle utilizes three receivers. Defensive tackles Alfred Collins and C.J. West, and linebacker Nick Martin also could get some playing time.

Saleh knows he needs patience with so many young players.

“They’re rookies. They’re going to have bumps,” he said. “But we’ve got to coach our butts off. The good news is it’s a really cool group of young men who are very deliberate in their approach. So, we have faith in the fact that as long as those boo-boos are in front of them, we feel like they’ll learn from those mistakes and continue to get better.”

Saleh returned to San Francisco this season after the defense he helped build regressed the past two seasons under coordinators Steve Wilks and Nick Sorensen. Saleh ran the defense for the Niners from 2017-20 before being hired as head coach of the New York Jets.

San Francisco ranked 29th in the league in scoring defense last season, allowing 25.6 points per game, and was tied for the seventh-fewest takeaways with 17. The Niners had just two takeaways over the final nine games and ended the season allowing at least 40 points in back-to-back games for the first time since 2015.

Jauan Jennings ready for opener

Receiver Jauan Jennings took part in his second practice this week after missing almost all of training camp with a calf injury and a contract dispute.

Jennings remains limited after missing more than a month, but is expected to play on Sunday barring any setbacks this week.

“Getting back into it, having all that time off we’ve got to ease him in and stuff, so we’ll see how this week goes,” coach Kyle Shanahan said. “That’s why he’ll be limited today. But he’s healthy enough to play football and hopefully that continues.”

Captains

The 49ers kept seven of their eight captains from last season with cornerback Deommodore Lenoir taking the last spot in place of Deebo Samuel, who was traded in the offseason.

The other captains are Warner, Bosa, QB Brock Purdy, TE George Kittle, RB Christian McCaffrey, LT Trent Williams and FB Kyle Juszczyk.

Roster moves

The 49ers signed WR Marquez Valdes-Scantling from the practice squad and signed WR Russell Gage to the practice squad a day after cutting him. Shanahan said both players could be active on Sunday.

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