CHARLOTTE — When the Panthers really dig into the work that has to be done to fix this defense, one of the biggest topics will be how to shore up a run defense that was last in the league.

One of the biggest parts of that process is already here.

Defensive tackle Derrick Brown, who was lost for the season in Week 1 with a knee injury, wasn't able to help this season but is already talking about being back on the field in OTAs this spring.

And he can't wait after what became the first extended absence of his career — other than the game in 2020 he missed with COVID-19.

"I was talking to my wife, and I told her I damn near felt invincible," Brown said Monday, as players cleaned out their lockers for the offseason. "So, a little reality check hit me this year. So it sucked to miss the whole season not to be able to be out there with the guys, especially since we knew we were going to have a tough challenge ahead of us and just not being able to help and contribute.

"It hurt at first, but being here with these guys, in the training room with the support staff, I mean, it's been awesome. I mean, they've been there for me through every single step of the way, and you know, I come in here and get to hang out with them and, you know, get to harass everybody a little bit and go on about my day."

Brown undersells his contributions. As soon as he was medically cleared to stand on the sidelines on game day, he was there. Even before then, he was around the team constantly, even on the days when he had to ride a motorized scooter to walk-through. But now, the assistance is gone; he's on his own two feet, and he's already thinking about the next steps.

"I'm good, you know. I'm halfway through the process of coming back, so I hope to be back by OTAs," he said. "Being here every single day with the training room staff has been good for me. I haven't really had a mental break with my kids. Just getting to do things that I don't normally get to do. I do a pick up and drop off and going to class parties, so we did a lot of things this year that I may not get a chance to do for a while."

As much as Brown might have enjoyed just being a dad, those who are around him on a daily basis know how hard it's been for him this year.

Center Austin Corbett has been like a rehab sherpa for Brown this season. While he was rehabbing his own torn biceps tendon, he was able to talk Brown through the process of rehabbing a knee. The same surgeon who repaired Corbett's torn ACL after the 2022 season (which included a lateral meniscus repair) did Brown's meniscus repair procedure, so Corbett made himself available to talk Brown through it.

And even in those conversations, Corbett sees the determination.

"He's been awesome," Corbett said of the way he's approached his rehab, which came months after the team committed to him with a contract extension in March. "I mean, you had a big contract, and freaking Week 1, it gets taken from you. It's tough, but he's a freaking fighter. Like it just lights a fire under him just every game, just having to sit back and watch and just see other guys, like that's the goal, that's what I gotta beat.

"I really want to be on the Panthers to make sure I don't have to go block him next year, because I feel like it's going to be pretty monstrous."

The good news is, among all the other upgrades the Panthers intend to make on defense, he's already in house, and a beneficiary of the stability that so many players talked about Monday. Building on what's already here was kind of a theme.

"Oh, he'll be ready, he's a pro, man. He's a hell of a player," guard Robert Hunt said. "I'm going to try to take my mind off it, but I know I've got to go block his big ass again. He's going to be ready, too. I wasn't looking forward to that this year, but having him back on the team is huge.

"He's a bad boy, so to get him back, he literally takes up two gaps. So excited to see what we can do with him. I'm really excited about what we can do."

But even in a vacuum, adding Brown back to the defense that allowed the most points in a single season in NFL history would be big.

He set an NFL record last year for tackles by a defensive lineman, and without him, the Panthers defense proceeded to allow the third-most rushing yards in NFL history. That wasn't all on him, but they know he can help fix it.

"It's big getting him back next year," cornerback Jaycee Horn said. "We know the main one of the main problems this year was just being able to stop the run. You lose a guy like that, and that's one of the biggest holes in the defense, so to get him back, I know the defense would be way better than this year. Just get him back alone."

Head coach Dave Canales referred to Brown's return as "a huge get for us," and longtime teammate Shaq Thompson could tell the immediate difference without him.

"He was a big part of his defense, a big part of that up front, he's a big part of us stopping the run," the veteran linebacker said. "Where you can get penetration and allow me and Josey Jewell just to play fast and go over the top, so that's one guy that definitely you need on that."

Again, Brown's a big part of the moving forward, but he acknowledged Monday how hard it was to watch the team fight without him following an offseason of personnel turnover on that side of the ball.

"Oh, it sucks," Brown said. "We know we had a lot of our big pieces missing. We went through the offseason, where we got rid of guys and were able to still have the core pieces we had and then lose them. I mean, that was tough."

But with Canales taking away the uncertainty of defensive coordinator Ejiro Evero's status — saying Monday Evero would return — they can get back to the building.

And with Brown talking about his return, they can do so knowing the cornerstone of the project should be back.

"We don't get to choose the cards we're dealt in this business," Brown said. "So I mean for us to be able to come out here, we had a plan, we just need to execute."

And he's ready to do his part.