SANTA CLARA, Calif. (AP) — The San Francisco 49ers went into the past few training camps with one of the NFL's deepest rosters filled with established stars that left little opportunity for rookies to contribute.

That's far from the case this year as San Francisco underwent a roster reset in the offseason that has infused the team with more youth and the most opportunities for rookies to compete since 2019 when draft picks like Nick Bosa, Deebo Samuel and Dre Greenlaw helped the Niners reach the Super Bowl.

That's especially true on defense, where at least five rookies are in the mix for starting roles on a unit that has been overhauled completely in the offseason.

“There’s a chance we could have six new guys starting. There’s a chance we could have eight, we’ll see how it plays out,” coach Kyle Shanahan said, referring to rookies, offseason additions and former backups. “Any time you say that, that’s different. That is a different team, that is a different side of the ball so that does take some time.”

The 49ers have had only four rookies start a season opener over the past five seasons, tied for the fifth fewest in the NFL in that span. They could match that this season with first-round pick Mykel Williams and fellow draft picks Alfred Collins, C.J. West, Nick Martin and Upton Stout all in the mix.

The Niners have started at least three rookies in a season opener just five times since the NFL-AFL merger, with the last time coming in 2006 when Vernon Davis, Manny Lawson and Melvin Oliver all got the nod. It also happened three times early in Bill Walsh’s tenure in 1980, the Super Bowl-winning season in 1981 and 1983. The most rookies to start an opener for San Francisco since the merger was four in 1978.

That's a challenge to a coaching staff that also includes a new defensive coordinator, with Robert Saleh returning after a stint as head coach of the New York Jets from 2021-24.

“With youth, the challenge is that a veteran never makes mistakes, but sometimes they might be a step slow," Saleh said. “They’re not running that 40 time that they ran back in the combine, right? Where a rookie is going to make a lot of mistakes, but he’s flat fast, and explosive. So, the trick is, how quickly can you get that football player to play like a veteran while he’s still connected to his 40 time that he ran back at the combine. So that youthful energy, that youthful explosiveness. With youth comes lumps because they’re learning.”

Saleh said even though his scheme isn't overly complex, he might need to simplify some things initially to help the young players acclimate.

The problem is the opposing offenses won't be doing the same and they will hope to confuse the rookies who aren't used to dealing with NFL offenses.

“They don’t just stand there and make it easy for us,” Saleh said. "They’re motioning, they’re moving, they’re jetting, they’re doing all kinds of stuff pre-snap. So there are going to be some moments where it’s like, oh God. But, you prick your finger, you fight through it, you get them to a point where they see it over and over and over again, and your hope is that that youthful explosiveness comes out as they continue to gain experience.”

The 49ers have liked what they have seen so far, with the young players being attentive in meetings and knowing their assignments on the field.

Shanahan said they have brought needed energy to the team starting in the offseason and the veterans have been impressed.

“I like the group,” Bosa said. “I think we have a lot of talent. I think when you look out on the field, you see NFL bodies out there that look impressive, which is a good thing. Obviously, we’re young, but I think just because nobody knows them now, if they play a good couple games, then the whole world will know them. It’ll be exciting.”

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