SANTA CLARA, Calif. -- In assembling their first free-agent class upon arrival in 2017, San Francisco 49ers coach Kyle Shanahan and general manager John Lynch weren't just looking for talented players. Just as important was making additions who were capable of helping to fix a broken culture.

So it was that Shanahan and Lynch began an aggressive roster makeover. Before free agency even began, they moved swiftly to sign steady veteran defensive tackle Earl Mitchell. On the first day of the new league year, they prioritized and landed the likes of receiver Pierre Garcon, linebacker Malcolm Smith, quarterback Brian Hoyer, fullback Kyle Juszczyk and kicker Robbie Gould.

Fast-forward two years and things have already changed dramatically. Despite posting just 10 wins in two seasons, the 49ers have a tight-knit locker room with young leaders rising. And with the emergence of those leaders comes the departure of those who preceded them.

San Francisco has already said goodbye to Mitchell and Hoyer and is poised to do the same with Garcon and Smith. In some of those cases, a lack of production was the impetus for the move, but it's also fair to wonder if the Niners would be as willing to part with so many veterans if they didn't believe in the young nucleus that has begun to grasp leadership roles.

If the disappointing 2019 season did nothing else, it allowed for youngsters like defensive tackle DeForest Buckner and tight end George Kittle to make their presence known in more ways than just the stat sheet. It was the season they took ownership in the franchise's future, a development Shanahan has called "extremely important."

“You have to bring in some people to plug in and do that," Shanahan said. "I thought guys did that, allowed us to get through that and kind of set a standard for certain guys. When you do that, you’ve got to have some young guys come up ... A lot of these guys have stepped up and made a role."

To be sure, the Niners still have dependable veterans such as left tackle Joe Staley and cornerback Richard Sherman who are more than capable of offering guidance to their many young teammates. Lest there be any doubt about where the future lies, one need only to look at the team's 2018 captains.

In his first year as head coach, Shanahan opted for a rotating cast of captains, eschewing the normal vote for a set group to handle those duties. Midway through this season, Shanahan decided it was time to establish that leadership. Staley, Sherman and Gould were slam-dunk choices, but Kittle and Buckner, in their second and third NFL seasons, respectively, were also chosen by their teammates.

By the end of the season, Kittle and Buckner had not only established themselves on the field -- they were the team's two best players all season -- but had a firm grasp on the concept that with that production comes more responsibility.

"I think that’s essential to winning programs and winning championships," Sherman said. "To be a winning organization, those have to be foundational pieces to what you do. Those guys set the standard and set the precedent for what other guys follow and I think that the organization is going to work to get more guys like that and follow their lead."

In Kittle and Buckner, the 49ers have ideal leadership complements.

Buckner's ascent, much like his personality, has been quiet and under the radar. Buckner has been one of the league's most dominant interior linemen for the past two seasons, but the Niners' record has prevented him from garnering much league-wide attention.

Still, as Buckner broke out with 12 sacks in 2018, the most telling moment of his season might have come after a Week 13 loss to Seattle, when he called out himself and his defensive teammates for failing to set the edge against the run consistently. Because Buckner isn't known for speaking out unless necessary, his words were taken to heart rather than cast aside.

Buckner has also been a more visible presence in the community, partnering with organizations like Beyond Differences to go to Leyva Middle School in East San Jose to help combat social isolation and bullying in schools. In December, Buckner took 20 student leaders from the school shopping for new clothes.

It's all part of the example he's hoping to set as a now-established team leader.

"DeFo just works," defensive lineman Arik Armstead said. "He’s also extremely talented and that combination of talent and work ethic, you become a good player. And I think he’s shown that throughout his career. He’s continued to grow, develop and get better -- and get better."

The boisterous, fun-loving Kittle offers a different but no less effective leadership style. While he thus far hasn't had occasion to call out teammates, he prefers to be unrelentingly optimistic, a persona that never changes from day to day. As Kittle says, the "glass is overflowing for me."

While Kittle is self-admittedly goofy, he has a no-nonsense approach when it comes to football.

"He was voted a captain because of his leadership as far as how he approaches football," Staley said. "... He hasn’t acted like he’s arrived, or he’s a superstar. He has all the right to, because I feel like he’s one of the best players in the NFL. He has that same kind of hunger and desire to get better that I saw with Frank [Gore] -- and the way that he worked on the practice field, was one of the hardest workers and super competitive."

The next step, of course, will be for the Niners to find more foundation pieces who can also step into leadership roles. That will be expected of quarterback Jimmy Garoppolo and will likely be something the team looks for in the No. 2 pick in this year's draft as well. As Kittle, a fifth-round pick in 2017, and Buckner, a first-round choice in 2016, prove, there's no blueprint for finding leadership.

"That can come in all shapes and sizes, and can come in all ages, and I think that's something that can't be lost on these guys," Lynch said. "Everybody can lead in their own way, and you get really good when you have a team full of leaders.”