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MIAMI — Sitting on the sideline at AmericanAirlines Arena after a December practice, Dirk Nowitzki couldn't help but feel nostalgic.

"Just walking in the building you have memories," he said. Some, he added, are painful, like losing to the Miami Heat in the 2006 NBA Finals.

But then he looked toward center court. "I remember holding the trophy right there," he said, gesturing to the Miami Heat logo. That was in 2011, when Nowitzki, playing the best basketball of his career, led the Dallas Mavericks to an upset Finals victory over the LeBron James, Dwyane Wade and Chris Bosh-led Heat.

The championship was the first and only title in Mavs history. It was a career-changing win for Nowitzki, one that validated all his hard work and sealed his spot among the game's greats. It also freed him to let his personal priorities govern the rest of his playing days.

"After that, I knew I was going to finish my career in Dallas. The only reason to ever leave would have been if we didn't win a championship that year," Nowitzki said.

"I think different guys have different priorities. For me, it was always important to be in one spot, one city. You know, the city I basically grew up in. I came here as a child. The city raised me. I always wanted to finish my career here."

Did he ever consider what it would be like to link up with another superstar elsewhere? He might no longer be an MVP candidate, but he's still a 7-footer averaging 12.3 points per game and shooting a career-high 42.9 percent from deep. His basketball IQ alone could elevate a borderline contender to a championship level.

And yet, Nowitzki has remained steadfast. He has no desire to chase additional rings, even after agreeing to cut his salary from $25 million to $5 million this season so the Mavericks could sign big-time free agents, which they failed to do.

"I mean, I don't really have an agent, so I'm not even sure how people get in touch with me," he said. He added that Kobe Bryant tried to recruit him to the Los Angeles Lakers once when he was a free agent—he can't recall the exact year—but he never gave leaving Dallas much thought.

Morry Gash/Associated Press

Nor did Mavericks owner Mark Cuban give much thought to dealing him.

"One time a decade ago when there was discussions of Kobe being on the trade block, [Dirk] said he would trade himself for Kobe," Cuban wrote B/R in an email. "I wouldn't."

But with the Mavericks struggling in recent years, have teams reached out about Nowitzki's availability?

"Of course," Cuban wrote. "We laugh."

There's no doubt Nowitzki, who holds a no-trade clause, will finish his career with the Mavericks. The only question is how much longer he plans to play.

Nowitzki arrived in Dallas as a timid 20-year-old German kid unsure of how to handle the NBA. He's played 20 seasons since, all with the Mavericks, tying him with Bryant for most seasons with one team. It's a record he'd love to hold by himself, but there are other factors that will influence whether he returns.

"The grind obviously gets harder every day. Maybe I'm done this summer—who knows?" he said. "You know, my body didn't feel great at the beginning of the season, but now the last few weeks it's felt a lot, lot better. So I'm actually encouraged by that, but we'll just have to wait and see how the rest of the year plays out."

It's not the games that wear him down but the training required to keep his body ready. For example, his family often travels in the summer, and he said, "You've got to find a random weight room in Kenya on a frickin' Monday—that's tough at times."

He continued: "So I'm kind of looking forward to those days where that pressure of always having to work out and stay in shape is gone. That's going to be a positive after my career."

Nowitzki paused for a moment, as if catching himself drifting too far into the negative. He jokes that he occasionally feels like an elder statesman, that "some of the social media stuff" makes him feel old and that he has "no idea who some of the young rappers are."

But, he said: "The playing is still awesome, still fun. It's tough at times; your mind sees things and wants to do things that are just not there anymore. Your body just doesn't respond the right way, but it's still fun. And I still like to compete with the guys—otherwise wouldn't be doing it if it wasn't fun. If I didn't think I could still help the team win some games, then I wouldn't be out here."

Still, at some point over the next few months, Nowitzki will have to decide whether it's worth putting in all that offseason work, especially for a team that's unlikely to compete for a playoff spot.

It was just under four years ago that a good friend of his asked him that same question.

Jae C. Hong/Associated Press

In April 2014, Nowitzki joined Steve Nash, his onetime Mavericks teammate, for dinner. The two have remained close. Nash was 40 years old and wrapping up his 18th season, this one with the Lakers. He had battled all sorts of injuries, sapping him of much of his burst.

And so, before a matchup with the Mavericks, Nash and his former teammate sat down for a meal.

"What would you do if you were me? Would you come back?" Nash asked Nowitzki in a conversation Grantland documented.

Nowitzki paused, seemingly unsure of how to respond.

"I'm not sure, bro," he said. "What you're going through, the treatments, in and out, I don't know if I could do it."

"He basically told me I should stop," Nash recently told B/R in a phone interview. "It was hard for me to accept what he was saying, but I appreciated [him]. As an athlete, you're usually the last person to know."

Nash said he and Nowitzki haven't spoken about Nowitzki's plans. They mostly just text. And, anyway, when to retire is a "really personal decision."

But if the two were to go out for dinner again, only this time with roles reversed, what would Nash say?

"I was in a different situation," he responded. "He's been brilliant in how he's been able to adjust as he's gotten older and the game's gotten quicker."

Pushed a bit more, Nash comes up with a more simple response.

"Play if you still enjoy it."

Yaron Weitzman covers the Knicks and NBA for Bleacher Report. Follow Yaron on Twitter, @YaronWeitzman, listen to his Knicks-themed podcast here and sign up for his newsletter here.