CHARLOTTE — If you want to know why the Panthers extended running back Chuba Hubbard's contract Thursday morning, you better be prepared to show up early. And to stay late.

As in, in the athletic training room before dawn, getting his body ready. As in, on the field three hours before kickoff every game day, catching balls from the Jugs machine in those lonely moments when he's the only player on the field. As in, an hour after every practice, going through his normal routine with his partner Tommy Tremble long after everyone else is eating lunch. As in, leaving in the dark again after putting in more than a shift.

In short, Chuba Hubbard works the way they want them all to work.

That's how he's turned himself from someone who used to be a liability in the passing game to someone they trust in every aspect. That's how he's turned himself from a fourth-round pick to a guy they don't mind investing another four years in.

"Years and years of work," Hubbard said earlier this year when asked about his ascension. "I mean, just staying diligent. Obviously, you're going to make mistakes. I think that's the best teacher out of everything. I've made more mistakes than I can count throughout these last few years.

"But, I pride myself on learning from them and just getting better, and I'm still going through that process now."

Even without the production — which is reason enough to sign him, he's fifth in the league in rushing — the Panthers made a statement by signing their starting running back Thursday morning before leaving for Germany.

When you're trying to build something lasting, you start with the people who work the way you want them all to work.

When former linebacker Dan Morgan took over as GM, his first move was to extend another foundational player, defensive tackle Derrick Brown.

While the two share few similarities, Brown and Hubbard are the cornerstones of their respective sides of the ball, the kind of guys coaches want teammates to look to.

Want to see how to work? Lead those sprint lines during OTAs like Brown. Want to know how to get on the field? Commit to improving your hands by catching hundreds of passes the way Hubbard has.

That's why the Panthers are willing to invest in him. Because he's invested in himself in a way that teammates notice.

"Chuba is unique, because he's a guy that it's really, everything is really important to him," veteran backup quarterback Andy Dalton said. "His game, how he goes about the recovery aspect, getting his body right, to studying and film and making sure he's knowing everything from not only the run game but the pass game to protections and everything.

"I mean, I feel like he's a special player and a guy that you can look at and be like, that's an example of how we want to do things. And I think that has allowed him to have the type of year that he's having so far, and we need to keep going with him because he's doing a lot of really good things."

And they clearly expect him to do those things in the future.

Having him here with Miles Sanders, Raheem Blackshear, and the upcoming addition of Jonathon Brooks gives them plenty of options in the backfield. And that kind of depth, preferably with complementary styles, adds layers to an offense.

When you want to run the way Dave Canales wants to run — stubbornly is the word he likes to use — having a back like Hubbard leading the way is a good place to start.

Hubbard has proven his ability to create something out of nothing, to make even the small runs productive, knowing that with time and effort, they can compound into something more.

"He's not afraid of the dirty 2- and 3-yard run, where you just kind of have to cram it up in there," Canales said. "And then later on in the game, they start popping into 8s and 12s, and here comes a 25. Just the discipline and his willingness to really commit to the system."

Hubbard committed to what it took years ago.

When he was stuck waiting behind Christian McCaffrey, he saw what the work looked like. And in those early days, passes to him were sometimes an adventure. So he decided to do something about it.

That's where the Jugs machine habit was born, and now, every Sunday morning, he takes the first bus to the stadium so a member of the equipment staff can shoot hundreds of passes his way, before many of his teammates arrive.

That's why the Panthers wanted to keep him here, and build around him.

He got to this point the hard way.

But his willingness to do the hard things on purpose was the point.