SANTA CLARA, Calif. -- San Francisco 49ers defensive end Nick Bosa was the NFL's Defensive Rookie of the Year in 2019 and has even bigger goals for himself as he enters his second season.

For Bosa, meeting those expectations figures to be more difficult after the offseason trade in which the Niners sent defensive tackle DeForest Buckner to the Indianapolis Colts for the No. 13 pick in last month's NFL draft.

Speaking to Bay Area media for the first time since just after the Super Bowl LIV loss to the Kansas City Chiefs, Bosa covered a wide variety of topics over the course of about 16 minutes and made it clear that replacing Buckner's production and leadership will be no easy task, even for a defensive line as deep as San Francisco's.

"Buck was definitely one of my best friends on the team and seeing him go is obviously bittersweet," Bosa said. "He got a pretty good contract and he deserves it but just losing him as a leader, we're going to have to really figure out how to step up and fill that void because he was the third down D-line play caller, he was the hype speech guy, he was everything. And I think he played with the best effort on the D-line, which really shows on tape when you see somebody that big sprinting to the ball every play and making those tackles downfield and obviously his pass rush ability, we're gonna have to step it up for him."

Buckner had been a key piece of the 49ers' rebuild from the moment they picked him No. 7 in the 2016 NFL draft. In four seasons with the Niners, he missed just one game, played the third-most snaps in the league and posted 28.5 regular season sacks. He was also a two-time team captain and won the team's Bill Walsh Award in February, which is given to the Niners player who "best represented the standard of professional excellence."

With Buckner now in Indianapolis, Bosa said the onus will fall on him and the rest of his linemates, including players such as Dee Ford, Arik Armstead, Solomon Thomas, D.J. Jones and Ronald Blair III, to keep the defensive line at an elite level.

The Niners also drafted South Carolina defensive tackle Javon Kinlaw with the No. 14 pick after trading down one spot from the selection they initially acquired for Buckner. Kinlaw is expected to step right into Buckner's spot as the three-technique defensive tackle.

Bosa hasn't seen a lot of Kinlaw but has been impressed with what little he's watched.

"He just embodies what we do as a D-line," Bosa said. "Just the way he plays the run, he's just a beast. He plays the run like we play it. He gets off the ball really fast and he's just a giant human, perfect to replace Buckner and I'm really excited. He seems like a good dude and I've been talking to him a little bit so I can't wait."

As for Bosa's own offseason endeavors, he admitted to taking some time to get over the Super Bowl loss before he was able to move on and realize that he will have more chances to win it in the future.

Bosa has spent his offseason at home in Fort Lauderdale, Florida, training with his brother Joey, in a strict regimen that involves waking up at 6 a.m., getting to a field in a nearby park for about 90 minutes of running followed by breakfast and then a trip to the gym owned by their father for more workouts that last until about 2 p.m.

"Honestly, my body is feeling unbelievable at this point," Bosa said.

After the 49ers drafted Bosa second overall in 2019, he quickly became a key cog in their turnaround. Bosa finished the regular season with 47 tackles, nine sacks, 16 tackles for loss, two fumble recoveries, two passes defended, an interception and a forced fumble. His 60 quarterback pressures were second-most in the league and he added four sacks and two forced fumbles in the postseason.

Despite that production, Bosa said Wednesday that he's hoping to "see the field a little better" in his second season. Bosa felt like he made some "little technique" errors that were visible on film.

"My expectations are always high and I set my goals really high and I've been achieving them so I'm going to just keep setting them high and just keep working my butt off and I know the work I'm putting in now is going to show up," Bosa said. "And I think I'm going to be a much smarter player next year and I'm just gonna know how to approach my opponents much better and I'm not going to waste rushes and make silly mistakes that I made last year and hopefully enhance my game."