SANTA CLARA, Calif. — After another loss to the Kansas City Chiefs, Nick Bosa wasn’t excited to go back and watch the tape. There was one thing he wanted to see, though: After the loss, his father, John, alerted him to how well rookie safety Malik Mustapha was playing.

As a defensive end, Bosa doesn’t get a chance to see those things in real time, but when he saw the film, he co-signed his father’s shot.

“He was like, Mustapha was flying and then I looked at the tape and saw that,” Bosa said. “It looked great.”

Nowadays, it’s not difficult to turn on a 49ers game and see a rookie succeeding in a prominent role. The team entered this season as the third-oldest in the league (with an average age of 26.9 years) and, in the past, has had little need for rookie contributions due to the large number of veterans on the roster. But due to an extensive injury list, the rookie class is quickly proving its value this season.

Last season, 49ers rookies played 1,760 total snaps in 17 games, with safety Ji’Ayir Brown leading the way in playing time (554 snaps).

Through eight games in 2024, San Francisco’s nine rookies have combined to play 1,665 snaps, which ranks seventh in the NFL. Guard Dominick Puni has played the most (549 snaps) of any rookie in the league in that span. And it’s been good: Puni ranks 14th among point guards in pass-blocking success rate (94.1%).

While injuries have hit the 49ers hard at safety, on both lines, in the secondary, and at running back and wide receiver, this youth movement wouldn’t be happening if San Francisco didn’t feel so good about the group as a whole.

“Honestly, I think this has been one of the most prepared groups of rookies we’ve ever had,” linebacker Fred Warner said. “It’s interesting because we haven’t had any rookies that needed to be ready to play, but now that they have their numbers and they’re ready, it’s been really good.”

Although none of the team’s rookies were expected to start or even necessarily push for a starting job, 49ers coach Kyle Shanahan was immediately impressed with the maturity and competitiveness of the group as early as May.

In the early days of training camp, the first wave of injuries hit San Francisco at the guard. Spencer Burford broke his right hand and Jon Feliciano had to deal with a nagging knee injury. Enter Puni, the third-round pick out of Kansas who had played all over the line and started 38 games in college.

That experience was quickly noted by Shanahan and offensive line coach Chris Foerster, who noted that Puni looked at home almost from the moment he stepped in with the No. 1 offense. Puni was so effective that even when Burford returned, there wasn’t really a decision to make: the job was Puni’s.

“That’s a perfect example for everyone,” Shanahan said. “You try to tell stories like that all the time to these guys. Don’t ever think of it as a redshirt year. There’s no such thing in this league. And it’s not just rookies, it’s the same for guys on the practice squad. Just usually there’s one injury, but sometimes it’s two, but it’s a matter of time. Some guys can get lucky and people stay healthy all the time and they can really develop the right way. But usually in this league, rarely. that is achieved.”

While Puni was the only rookie to start Week 1, Mustapha, a fourth-round pick out of Wake Forest, joined him in Week 4 after playing 83 snaps in the first three weeks.

Like Puni, Mustapha has played well, recording 29 tackles, one interception and two pass deflections. According to NFL Next Gen Stats, Mustapha has been targeted 10 times in 138 coverage snaps. He has allowed a 20% completion percentage (the best mark for any NFL player with at least 50 snaps) for 27 yards and a touchdown.

He could keep the job for the rest of the season depending on whether Talanoa Hufanga can return from a torn ligament in his right wrist. Others, like second-round cornerback Renardo Green, who appears to have overtaken Isaac Yiadom at third cornerback, fourth-round running back Isaac Guerendo and seventh-round linebacker Tatum Bethune, have played more than 100 snaps.

And that’s not even taking into account the two receivers selected (first-round pick Ricky Pearsall and fourth-round pick Jacob Cowing) who have now had expanded roles following injuries to Brandon Aiyuk (torn ACL and lateral ligament right), Jauan Jennings. (hip) and Deebo Samuel Sr. (pneumonia symptoms, ribs and obliques).

After recovering from a gunshot wound suffered during an attempted armed robbery in late August, Pearsall was activated from the non-football injury list prior to the 49ers’ Oct. 20 game against Kansas City. He made his first NFL start the following week against the Dallas Cowboys and will play a pivotal role the rest of the way, even when Samuel and Jennings return.

Aiyuk’s injury and Samuel’s illness forced Pearsall to play more than expected, and he finished with 77 yards from scrimmage against the Cowboys. The week before that game, Mustapha approached Pearsall and told him it was time to make his mark.

“[He] “I said it perfectly, just being the cherry on top of it all,” Pearsall said. “I think ever since we were drafted and seeing the guys we picked, I knew we had a strong class. … Unfortunately, I got to watch everyone perform from the bench, but I still got to see all the talent that this rookie class has “I’m excited to be able to add something more.”

At 4-4, the 49ers are waiting for some of their most important injured players, such as running back Christian McCaffrey, who began practicing this week before Sunday’s game against the Buccaneers (1 p.m. ET, Fox), linebacker Dre Greenlaw, kicker Jake Moody and potentially Hufanga will return in the final two months of the season.

That could cut into the playing time of some of the rookies, but as you’ve already learned, your number will be called again. That’s why left tackle Trent Williams, who is in his 14th year in the NFL, calls it the “most productive” class of rookies he’s ever encountered in his career.

And as Williams points out, this rookie class will eventually become the next generation of players the 49ers are counting on to stay competitive in the future. That is yet to be determined, but early results are promising.

“It’s always important to get your draft picks right,” Williams said. “That’s the only way to keep the locker room improving, trimming the fat… Even though we have a lot of high-net-worth players, the draft picks are really the lifeblood of the team year in and year out. So it’s extremely important.”