NEW YORK — Dirk Nowitzki can’t run these days, a victim of a nagging Achilles that is driving Mr. Maverick up the wall. Out for six of Dallas’ first nine games, he sees his depleted team already losing ground in the Western Conference and can’t do anything about it.

“It hasn’t been fun sitting and watching — and watching us lose,” he said.

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However, he did manage to smile — broadly — when the subject turned to his new teammate, Harrison Barnes, during a recent interview with Sporting News. This was after the Mavs, minus Nowitzki, Deron Williams and Devin Harris, mustered all of 77 points against the Knicks, one of the NBA’s worst defenses. After signing some sneakers and Mavs paraphernalia for Ben Stiller, one of many celebrities hoping to see Nowitzki play in his favorite road venue, Nowitzki paid Barnes the ultimate compliment.

Nowitzki said Barnes can step into his shoes when the 38-year-old retires.

“He has the complete package,” Nowitzki told SN. “I’ve worked out with him a couple of times after practices, and he’s got every shot in the book. And he’s looked like a franchise player here the last few weeks. He’s shown us moves that are very impressive, not only shooting the ball, but driving the ball, both ways. He’s got left(-hand) hooks and left runners. He’s shown strong post moves. He’s athletic. He’s a hard worker. He wants to win. So I think the sky is the limit for him.”

Barnes is off to a strong start. He’s averaging 22.3 points a game on 49.1 percent shooting, a clear-cut first option for a team in desperate need of one. Removed from the Warriors’ switch-heavy system (and Defensive Player of the Year Draymond Green), his defensive metrics have taken a dive, and he has dropped below an assist a game despite having the ball more frequently. But the Mavericks have been substantially better (9.7 points per 100 possessions) with Barnes on the court than without.

It’s clear that the 24-year-old was ready for more than being the Warriors’ fourth option. More up for debate is whether he’s a franchise player or merely a building block.

As one veteran scout told SN, “Nowitzki is going to the Hall of Fame, and Barnes shouldn't be mentioned in the same breath with him. It's not even clear Barnes is a prime option on a contender. Is he a No. 1, No. 2 or No. 3 option? All we know is that on Golden State he was a complimentary player. He was a very good role player, but not a go-to guy. When you break down his skills, it's hard to say he's truly elite in any of them. He's a decent shooter, a pretty good rebounder, an adequate scorer, a good defender, and nothing special as a passer. So where's the greatness?”

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Now in his 19th season, Nowitzki has set a high bar for Barnes. The Mavs made their only two trips to the Finals (in 2006 and 2011) and won their only title in 2011 because Nowitzki carried them there. He’s the reason they’ve been to the playoffs 14 out of the last 15 seasons, as he’s climbed the all-time scoring ladder to his current No. 6 position.

Nowitzki’s best supporting cast was with him before he did all of his big winning, when the Mavs had Steve Nash running the show and had Michael Finley slashing from out on the wing. Then Nash returned to Phoenix, and a year later, the Mavs decided that Finley was done and waived him.

“So when I took over, it was kind of by default,” Nowitzki told SN. “It was always Steve and Mike and myself at the beginning. But then Steve leaves and Mike is gone and the next thing you know, I was the only guy still out there. So it was my team and I took it and ran with it. At the beginning, when you’re “the guy’ it’s different. You have to work through stuff and you make mistakes that you regret, but you learn from those. You get better. Harrison has shown he can already do that.”

To become Nowitzki’s heir, Barnes will have to show the kind of mental toughness that Nowitzki made famous. He had come back from back from several gut-wrenching playoff failures, from 2007-10, to make Dallas NBA champions. Can Barnes carry a team, night in and night out? So far, Nowitzki has seen what he likes.

“The thing is, a player has to be put in that position to find out if he can be that player and deal with all the mental stuff,” Nowitzki said. “And he’s been doing that for the first few weeks. He’s been playing a strong game, knowing the team is counting on him, as I’ve been out and other players have been out, too. So far, he’s stepping up in the locker room and talking after games about what has to be done. He’s doing what you want to see. We’ve loved everything we’ve seen so far.”

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The No. 1 thing? Barnes hates losing, and he’s done more of that in his first three weeks in Dallas than he did in the first five months of last season with the Warriors.

“Losing sucks,” he said. “There is no joy in it.”

From owner Mark Cuban to team executives and teammates, the Mavericks love that Barnes comes off losses working harder and trying to improve. He’s had plenty of opportunities to do those things, as Dallas started off the season with a franchise-record five-game losing streak and has lost seven of its first nine games. They play the Celtics in Boston on Wednesday, and it’s likely that Barnes won’t be able to team with Nowitzki once again. So again he’ll take the floor as “the man” in what is clearly more than an audition. It’s his job to lose.

“It’s something I’m prepared for,” he said. “I feel like I’m comfortable stepping into that. But in the current state, all I’m concerned about is getting wins. We’re in a situation where we’re in the West and obviously, it’s a very difficult conference. If we don’t get some wins, we’re going to put ourselves in a difficult situation.”

But this is a good testing period to see what Barnes can do, after spending his first four seasons with two-time MVP Stephen Curry and All-Stars Green and Klay Thompson. He officially became expendable after the Warriors collapsed against the Cavaliers in the Finals, as he and center Andrew Bogut went to Dallas while the Warriors opened up cap space to get Kevin Durant.

The Mavs at the time were scrambling after striking out in free agency for Hassan Whiteside, Mike Conley Jr. and Nicolas Batum. So they went back over Barnes’ career and were struck by his first playoff season, when he sometimes outplayed Curry and the other Warriors against the Nuggets and Spurs, under coach Mark Jackson.

“We felt like he was a system player who, when you gave him the opportunity to be himself, he could be much bigger and much better,” Cuban said. “He played to the system. Now he has to be the system. So that will be his challenge. Does he have that f— you in him?”

Nowitzki sure did. But as he’s aged, he’s been more suited as a No. 2 option. He was a groundbreaking 7-footer for more than the shooting that stretched the defenses to the three-point arc with his astounding range. His greatness was seen in the fact that although he could score from just about anywhere on the court, he was probably the first true big who forced defenses to come away from the basket and double-team him at the elbow.

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At 6-8, Barnes will have to be a different kind of threat and prove he can score or make plays for teammates when defenses load up against him.

“His next step will be to figure out how to play out of double-teams, because he’s never really experienced that,” Bogut said. “But from what I’ve seen from him over the years, he’ll get better and better. He’s done that every year he’s been in the league. He puts the work in. He looks after himself off the floor. He’s not out every night. He really takes care of his body. He’s big on his recovery. He’s a true professional. He’s got a great chance to become that player.”

Correction: An earlier version of this article identified Ben Stiller as Ben Affleck.