CHARLOTTE — It's easy to say, "Next man up."

It is decidedly more difficult to implement it, and have it work.

But the way the Panthers train their defense at least gives them a chance to survive a recent run of injuries, which threaten to slow down a hot start to the season. They're not going to use them as an excuse, because they've conditioned themselves to embrace the need to adapt.

"The standard remains the standard," safety Jeremy Chinn said this week, as the 3-0 Panthers prepare for Dallas. "Whoever's on the field, it's always going to be the same standard. Guys are going to have to step in and step up.

"But the standard is the standard, and we all believe that and we all know that, and that's what we're going to hold ourselves to."

And so far, the bar has been set pretty high.

The Panthers currently rank first in the NFL in total defense, rushing defense, passing defense, and sacks. Perhaps the most impressive jump they've made in the first month of the season is in third-down conversions. 

A year ago, they were next to last in the league, allowing just under 50 percent of every third down to turn into a first down. 

This year, they're leading the league at a 21.2 percent clip (7-of-33). 

That doesn't happen by accident. And it's not going to be easy to maintain.

Last week, they lost rookie cornerback Jaycee Horn to a broken foot which will knock him out at least a couple of months, if not the entire season. They also lost veteran safety Juston Burris to a groin injury that landed him on IR (meaning he'll miss at least three weeks). Those two came after they lost nickel Myles Hartsfield to a dislocated wrist in the opener.

That's a lot of stuff.

The hope is that the guys left behind can continue to play at a similar level, because that expectation is something they've spoken into existence.

They still have Donte Jackson, who is playing his best football. They do get cornerback A.J. Bouye back on the field this week. And they're trying to train trade acquisition CJ Henderson up so he can play a role, if not this week. But mostly, this will fall on safeties Sam Franklin Jr. and Sean Chandler, and veteran cornerback Rashaan Melvin and youngsters Keith Taylor Jr. and Stantley Thomas-Oliver III to keep things going.

"I mean, the standard was set back in the offseason," Jackson said. "We know what type of toughness, and hard play that comes with being on this defense. I definitely think it trickles down. It doesn't just stay up at the top, or stay with the starting lineup. It trickles down all the way through the depth chart.

"So I definitely trust every guy who is going to be out there with us. I trust everybody to know what they're doing. I trust everybody to play physical. I trust everybody to fight for 60 minutes."

Part of that confidence comes from the way they train their secondary.

Defensive passing game coordinator Jason Simmons explained that they don't panic over trying to replace guys, because they try to cross-train all their defensive backs anyway. So when Hartsfield went down in Week 1, the pressure to find another nickel wasn't as great since other players had gotten reps and classroom work on the assignment.

"They're different jobs, but we just say everyone's a football player," Simmons said. "We don't look at it that way, that each job is different. You're a defensive back, you're a defensive back. You play all the positions back there. That's the luxury of training those guys like that in OTAs; it's helped us out."

Simmons said that the building block of defensive coordinator Phil Snow's system starts with teaching an overview of the entire defense.

"We teach guys coverage," Simmons said. "So if they understand the overall global structure of the defense, they know how everybody fits in it. That's the thing that's really helped us, I believe.

"If we're in our true coverage where we're rushing four and dropping seven, we make sure everybody understands what all seven in coverage are doing. Whether that's cover 4, cover 3, man, if you don't understand what everybody's doing, you don't understand the weaknesses of every coverage, and where the snakes are."

The snakes might be numerous in Texas this week, as they're playing against a Cowboys offense with a smart quarterback in Dak Prescott, who has plenty of skill-position talent around him. As they showed Monday night when they dropped 41 points on the Eagles, the Cowboys can score in a hurry. But Prescott's ability to read a defense and adjust is different than what they've faced so far this year. It's one thing to confuse a rookie making his first NFL start; Prescott's a different problem.

And having to do it all without Horn makes it that much more difficult.

Snow acknowledged as much recently, by noting exactly what they're missing without Horn.

"I mean really in the game, do you even know he's in the game?" Snow said of the first-rounder. "He takes his receiver out of the game. I mean, the first three games, it's been a pleasure to watch him play."

Now, they have to do it without him.

"You're going to have to do business differently; he's a really good player," Snow said. "We have guys that will fill in and play hard and do what they're supposed to. But when you lose really good players you have to adjust what you're doing and how you're doing it. We just have to adjust. . . .

"I told the players before New Orleans, if we're coaching you every day, I expect every player in the room to play at the standard we expect. When you're going into the game, I'm going to call it the way I call it, no matter who is in the game."