SANTA CLARA, Calif. (AP) — A new defensive coordinator, an infusion of youth and the return of Dre Greenlaw had San Francisco 49ers star linebacker Fred Warner raving about how much fun he was having anchoring one of the league's more surprising units this season before heading out on the bye.

Warner's enthusiasm, and the potential of the Niners defense, only got higher after the team made a big move during the week off to bring back three-time Pro Bowler DeForest Buckner to help anchor the defensive interior.

“I just love the blend of obviously the older veteran leadership, as well as the younger guys that have asked to play a lot of snaps, who are out there competing their tail off," Warner said before the week off.

"The blend right now is great. We obviously have to get healthy to have all of our weapons out there to help us compete to win these games. It’s always next-man-up mentality. No matter who’s out there, we have to be able to compete and execute our job at the highest level. So, we’ll be better.”

San Francisco has been very good for most of the first half of the season under first-year coordinator Raheem Morris as the new wrinkles he has added have paid off with more aggressive play from the secondary, an improved run defense and more pressure on the quarterback.

The 49ers went into the bye ranking third in the NFL allowing just 3.48 yards per carry — down significantly from last season's mark of 4.32 — have allowed a league-low five runs of at least 10 yards and already have 15 sacks after generating a league-low 20 last season.

The Niners have done all that despite playing without star defensive end Nick Bosa for the past five games, and missing several other projected contributors such as Mykel Williams, Alfred Collins, C.J. West and Sam Okuayinonu for significant time.

“I thought we’d have a chance to have a real good defense this year, but I think I’ve said earlier, so I’m not trying to beat a dead horse, but when you lose (so many) D-linemen in the first two weeks, if you told me after that we’d still be a top-five defense, yeah I would have been a little surprised," coach Kyle Shanahan said.

"I think it’s a credit to everyone who has stepped it up. It’s a credit to Raheem and the rest of those guys on the coaching staff. I’m real happy with how they’ve been working and playing and finding ways to win.”

The defense was exposed a bit in the final game before the bye when Michael Penix was able to get rid of the ball quickly to avoid pressure and throw for 213 yards and three TDs, while committing no turnovers, taking no sacks and not being under pressure once.

But the front has been a pleasant surprise thanks to the addition of Osa Odighizuwa in the offseason, promising play from rookies Gracen Halton and Romello Height and Morris' ability to create pressure by using more five-man fronts and blitzing at San Francisco's highest rate in six years.

“I think it’s a little less about me creating pressure. I think it’s just about the guys executing the game plan," Morris said. “We’ve got some really good people up front doing different things. I know you’ve heard it before, but you’ve got to rush as a unit. When you don’t have that superstar player that we know we’re missing, like a Bosa, you’ve got to be able to rush as a unit.”

The task should be much easier after the bye with Bosa expected to return and the addition of Buckner.

Bosa is the 2022 AP Defensive Player of the Year who has been extremely productive when healthy throughout his career with his average of 0.74 sacks per game ranking seventh best since he entered the league in 2019.

Buckner and Odighizuwa are two of 16 interior defensive linemen with at least 20 quarterback pressures this season.

With those three anchoring the line, role players such as Keion White and young players such as Halton, Height and Williams can provide the depth to give San Francisco a formidable front.

“You never really want to go through adversity,” Morris said. "Everybody says they want to go through it. But, when you do go through and you get a chance to watch your guys go out there and respond, that is something that forms teams and that’s something that you need at any time during the season. ... Watching these guys go out there and different people step up in different roles and do different things, whether it be because of injury or just because of the situation of the game, I think those things are always key and critical to develop during the season.”