CHARLOTTE — Perhaps you've noticed, the Panthers have had to deal with some injury problems this year, particularly on defense. The fact they've still played at a reasonably high level has kept them competitive, but it's also remarkable considering the number of replacements they're dealing with.

They had high hopes on defense this year, based largely on guys such as Brian Burns and Jaycee Horn and Shaq Thompson, along with new safety Vonn Bell coming in to lead the way. But last week against the Bears, those first three spots were filled by rookie pass-rusher DJ Johnson, a cornerback originally signed to the practice squad after the Chiefs cut him in Dicaprio Bootle, and a journeyman linebacker Kamu Grugier-Hill. who came here to be a backup. And two weeks ago against the Colts, it was Alex Cook, an undrafted rookie who was recently signed off the Giants practice squad, starting in Bell's spot.

Among others. It's been that kind of year.

"So like, 'next man up' is almost a way of life," Johnson said with a grin because it has had to be for the Panthers this season. "It's something that you don't just prepare for, something that you're constantly preparing for.

"Something my coach says a lot that I like is that you got to look at it like we're all starters, we're all starters when you get put in, you got to know that they're speaking at the same level as the original starters. So having that mentality and embracing it, that's what I mean."

Playing that way doesn't just happen, though. Being able to survive all the changes they've had to endure this year — they haven't started the same 11 in back-to-back weeks yet this season — takes a lot of adjusting and a lot of intentional work. So, from playing what amounts to a one-linebacker system at times or just swapping guys out mid-game, defensive coordinator Ejiro Evero and his staff have had their hands full this year.

"It's so much about the nature of the NFL; people are going to get hurt, and everybody needs to understand that, players and coaches. And if you're not coaching the bottom part of your roster as much as the top part of it, you're going to get burned," Evero said. "We try to preach that message, and we try to get the guys to buy into it that, hey, even if you're not playing a lot and your playing time is not meeting your expectations, you've got to stay ready because the last thing you want to do is you get your opportunity, and you're not ready."

Evero made sure to spread the credit around to his assistant coaches, saying, "they're all great teachers." And certainly Todd Wash (defensive line), Tem Lukabu (outside linebackers), Peter Hansen (inside linebackers), Jonathan Cooley (cornerbacks), and Bert Watts (safeties) have all done a good job this year, along with assistants Bobby Maffei, Mayur Chaudhari, and DeAngelo Hall.

"What ends up happening a lot is obviously our position coaches are really dealing with the player, the ones and the backups, but when we bring you guys in it's our quality control coach or assistant coaches that are really spending that extra time with them on the back on the background, to get them caught up," Evero said. "And so I just think it's just been unbelievable teaching job by our coaches, and they're way more important and involved in that than I am, to be honest with you. So it's a credit to the coaches."

Johnson said that specifically, he's been impressed with how detail-oriented this staff has been — he deals with Lukabu mostly and has adopted his sayings — when it comes to getting him and the rest of the replacements ready. Grugier-Hill said that in position meetings, they're all careful to talk to the room as a whole instead of particular players since the lesson that applies to one applies to all.

"They're all very detail-oriented," Johnson said. "So like just that alone, when you see a coach that's always on the detail, you embody that. A perfect example is like the first thing you're taught when you come out here is stance, alignment, key, technique, responsibility. So the first thing I was taught when I came here was that just knowing exactly what everything you need to know was, and then just playing football."

Of course, coaches are always trying to make sure guys are prepared, but it is more complicated when you never know who you're dealing with from day to day.

When Cook had to start the other week, there was some uncertainty as to whether Bell was going to be able to come back to play after a quadriceps injury. He was trying to practice, but they didn't know if he'd be available. So when they went out to practice Wednesday, Watts told Cook to go out there alongside Xavier Woods with the ones. There was no grand announcement. Just go, it's your time.

"He just said 'Woods, AC, go,'" Cook recalled of that day in practice. "I was like, cool, and he kept saying it, and he kept saying it, and I kept being the guy every single day. I think it helped me that they didn't say I was the guy because I might have put a lot of pressure on myself at the beginning of the week.

"They're just letting me get the ones reps and kind of getting acclimated and getting adjusted with the guys I'm on the field with. They just let me just be me, I guess, and just threw me out with the wolves, but that's been the story of this season, though.

It was a lot to process, especially for a guy so new here.

"I really had to take a step back for a moment and just remember that football is the same game I've been playing since I was seven, no matter what stage I'm on," Cook said. "I was the next man up, but I've still got to execute. They're looking at me; I'm a rookie. I'm an undrafted free agent who just came to a new team, got a start in the game, and I haven't even been here for two weeks. I mean, outside looking in, you say that's a lot.

"But as somebody who takes a lot of pride in his work and his craft, you've got to have that same expectation, the same standard that must be upheld as the guy who was there before you. I can't let my teammates down; they're dependent on me.

For a guy like Bootle, who spent two years with the Cheifs before signing to the practice squad here in September, there was a little more familiarity with the way the league works. But he's still stepping into a position generally filled around here by high picks. Horn and CJ Henderson were guys chosen in the top 10, and Donte Jackson was a second-rounder. But with two of them out, the undrafted guy from Nebraska has to carry the same responsibility.

"As a pro, it's your job to understand that all it takes is one or two players going down, and you've got to go out there and execute," Bootle said. "So with every rep that you get, whether it's the first rep of individual (drills) or whether it's the first rep of practice against the offense, you've just got to go out there and make sure you execute your assignment because it translates to the game.

"You either take it seriously and shine when it's your moment, or you treat it poorly and you don't execute to the standard of the team or the defense."

Both Johnson and Grugier-Hill described a feeling resembling fear, times when they were younger, and the realization that their time could come at any time dawned on them that not being prepared would leave them exposed.

"I think when you're a younger player, it's easy to kind of just be like, oh, I'm just going to worry about special teams or whatever, and then something happens, and you get thrown in, and you're just not prepared, right?" Grugier-Hill said. "So as I got older, I realized I have to be ready no matter what, and it helped me. Even going in this year, I went into the mindset, hey, I'm going to support Shaq, like, I'm going to watch my film. I'm going to do this and give him pointers. So that helped me, right? Be prepared because I'm looking at it as if I was him. So then, when he went down, I think I was prepared mentally, at least.

"I actually was lucky. I didn't really have any moments early in my career where I had to go in on short notice, but I knew just who I was at the time. If something was to happen, I was not prepared."

Grugier-Hill's in his eighth season in the league now, so it's clearly something he's learned.

And if he hadn't, this year would have been all the lesson anyone needs.