Nerlens Noel and the Mavericks seem headed for an ugly divorce. Noel turned down a contract extension worth four years and $70 million in the offseason, according to his former agent, and instead signed a one-year qualifying offer that will make him an unrestricted free agent next summer. Both sides said the right things about making their relationship work in training camp, but it has quickly deteriorated this regular season. Noel played only six minutes in a win over the Wizards on Tuesday, and he received a DNP-CD in a loss to the Cavaliers on Saturday. The Mavs are one of the worst teams in the NBA, and Noel has still fallen out of the rotation.

There’s no room for another traditional center in the Mavs’ starting lineup. Opening with Noel moves their other key players out of their best positions. Dirk Nowitzki is 39 years old and in his 20th season in the NBA, and he no longer has the speed to play power forward. Harrison Barnes has been much better at power forward than small forward in two seasons in Dallas, where he can use his strength to match up with bigger players in the post on defense and then take them off the dribble on offense. It’s the same story for Wesley Matthews, who is better with a speed advantage at small forward than a size advantage at shooting guard. Noel has started in six games this season, which moves Nowitzki to the 4, Barnes to the 3, and Matthews to the 2. That lineup, with rookie Dennis Smith Jr. at the 1, has a net rating of minus-16.7 in 47 minutes.

Nowitzki is on his last legs in the NBA, but it’s almost impossible for coach Rick Carlisle to bench him. The Mavs don’t want Nowitzki breaking a sweat in warm-ups and then immediately stiffening up on the sidelines during the first few minutes of the game. He’s an icon with a powerful connection to a relatively fickle fan base that has little reason to come to games or follow the team besides a desire to watch him in what could be his final season in the league. Nowitzki is averaging his worst numbers in points (10.5), rebounds (5.5), assists (1.4), blocks (0.3), and field goal percentage (42.1 percent) since his rookie season. He would probably be better in a smaller role on the second unit at this stage in his career, but the Mavs want to honor a player who has meant so much to the franchise and the city of Dallas. There are more than a few similarities between Nowitzki’s final seasons and the way Kobe Bryant’s career ended in Los Angeles. Only a select number of players get to leave on top like Tim Duncan.

Dirk is averaging 24.2 minutes per game this season, which still leaves half the game for Noel. However, Dallas has one of the most imbalanced rosters in the NBA, with seven centers, five point guards, and only three wings. The competition for playing time upfront is fierce, and Noel has not earned Carlisle’s trust. For every spectacular block and dunk, he will miss a defensive assignment and gamble for a steal that exposes the defense. Carlisle is an old-school coach who has traditionally been hard on young players. He has little patience for guys who make mental mistakes and don’t accept their role.

“The number one job in coaching is to keep role definition simple and decisive and make sure everyone knows their job,” Carlisle said when I asked him about what he wants his centers to do on defense. “A system means there is help built into it as long as you do your job. If you go outside the system and start breaking rules willy-nilly, then there’s not going to be help built in for you, and then there’s problems and you have to get guys out of the game.”

The Mavs don’t have a lot of talent. They need all five players working as a unit to succeed. Noel has the worst net rating (minus-20) of any player on their roster, and their defensive rating is 9.5 points better when he’s off the floor. He’s at his best when he can extend out on the perimeter and keep smaller players in front of him, but Dallas needs their centers to hang back in the paint on pick-and-rolls. According to the tracking numbers at Synergy Sports, Noel is in the 13th percentile in the NBA this season when defending the roll man. While he has quick hands and a great career steal rate for a center (2.9 percent), he’s still learning how to be aggressive without taking unnecessary risks, and the Mavs don’t have the personnel to protect him when he freelances. Noel has had too many plays like this one against Memphis, where he goes for a steal on Marc Gasol and then bites on a hesitation move by Mike Conley, allowing Conley to get into the lane and draw a blocking foul:

Like a lot of young players, Noel’s energy level can depend on how much he’s involved on offense. In Carlisle’s spread pick-and-roll system, the 5 is supposed to set a solid pick at the top of the key and then roll hard to the rim, collapsing the defense and opening up a driving lane for the point guard and easy kick-outs for the other three guys at the 3-point line. It’s a hyper-specific role that doesn’t allow them to showcase their full offensive game. Noel is a fairly skilled passer, but he rarely gets the opportunity to do so in Dallas. Responsibility has to be earned. Carlisle tweaks things to make Dirk comfortable, but he’s not going to do that for an unproven young player who hasn’t shown he can handle a smaller role. It’s a self-fulfilling prophecy: Noel doesn’t get a lot of touches so he’s not as engaged mentally, and both sides get frustrated with the other. There have been several instances this season where Carlisle has pulled Noel out of the game just to yell at him for not running the floor hard.

Rick Carlisle pulled Nerlens Noel. "You weren't running until I f------ yelled at you! C'mon!" Then sent him right back to scorer's table. — Tim MacMahon (@espn_macmahon) October 29, 2017

Noel has lost playing time to Salah Mejri, a 31-year-old from Tunisia in his third season in Dallas. Unlike Noel, Mejri has embraced his role on both sides of the ball. He sets solid screens, rolls hard to the rim, competes on the boards, and protects the rim. He has the best net rating (plus-4.5) of any big man in their rotation, and he has been far more productive on a per minute basis than Noel:

Salah Mejri vs. Nerlens Noel (per-36 minutes) Per-36 minutes Points Field Goal Percentage Rebounds Blocks Per-36 minutes Points Field Goal Percentage Rebounds Blocks Mejri 10 70.6 15.7 5.4 Noel 11.6 53.2 11.7 1.8

Carlisle didn’t hold back when asked about Noel’s playing time after his DNP-CD against Cleveland: “Minutes have to be earned,” he said. “If it’s between him and Salah, Salah has earned the minutes. There’s no doghouse here. It’s pretty simple. You compete, and if you earn minutes, you get minutes. And you’ve got to compete to keep them, because it’s a competitive situation.”

Of course, if Noel had signed an extension with Dallas in the offseason, Carlisle would have made more of an effort to put him in a position to succeed. Locker-room politics and financial considerations play a role in determining playing time on every team in the NBA. The Mavs have spent the past three years trying to turn Dwight Powell, a power forward in college, into a stretch 5. Powell is averaging 3.9 points per game on 34.5 percent shooting this season, but they are giving him every chance to play through his mistakes. He signed a four-year, $37 million contract for the Mavs before the start of last season. Dallas has more of an investment in Powell than Noel, and there’s no reason for a rebuilding franchise to prioritize a player who might be gone next season over someone who’s there for the long haul.

Noel, for his part, has handled the situation professionally. He appears to have learned from his time in Philadelphia, when he complained to reporters about losing minutes to Joel Embiid and Jahlil Okafor. He is almost always available to the media after games, and he doesn’t show any frustration when peppered with questions about his playing time. “I’ve just been focused on doing what I do. I’m keeping everything simplified. Things are going to come, things are going to play out. I’m really focused on getting better and supporting my guys,” Noel said after the Cleveland game. “I know I can go in there and change games. When my number is called, I’ll do just that.”

Noel is still looking for the right fit in the NBA. He was the victim of a numbers crunch at center in Philadelphia, and the same thing is happening in Dallas. He has never played with a high-level point guard who can command the attention of the defense and make the game easy for him. While Smith has show flashes of greatness in his first season in Dallas, he’s still a 19-year-old learning how to play the position. The Mavs were hoping Noel and Smith could form a dynamic pick-and-roll tandem for the next decade, but they weren’t willing to break the bank on a 23-year-old with health concerns. Noel has struggled with injuries over the course of his NBA career, and he hasn’t put on much weight since leaving Kentucky. His thin frame (6-foot-11 and 220 pounds) means his body may not be able to handle the rigors of banging an entire game against some of the Goliaths at center in the West.

There’s still time to repair the relationship. Noel played well after the Mavs acquired him at last year’s trade deadline, and they clearly thought he would be their center of the future when they offered him a big contract. He will eventually get another chance since Dirk won’t play 82 games this season. However, with Mejri playing well and so many other centers ahead of him, he has his work cut out for him. While the Mavs’ dream of pursuing DeMarcus Cousins in free agency looks pretty hopeless at the moment, they will likely have a high first-round pick in the 2018 draft, in which several highly regarded young centers (Deandre Ayton, Mohamed Bamba and Marvin Bagley III) will be available. Dallas didn’t give up much (Justin Anderson, Andrew Bogut, and two second-round picks) to acquire Noel. It was a low-risk gamble that hasn’t worked out, and there doesn’t appear to be hard feelings on either side.

The Mavs are open to moving Noel, and a trade might make sense for everyone. He’s a young almost 7-footer with elite athleticism and more offensive ability than most guys with his physical tools. Big men take longer to develop than guards, and it can take them a while to find the right place in the NBA. Part of the maturation process for young players means accepting what their role will be in the league. When Dallas traded for Noel, someone in the Sixers organization told me he was a situational center who thinks he’s a star. Noel reportedly asked for a max contract this offseason, and he won’t get one after what has happened this season. But there’s nothing wrong with being a situational center. A situational center can look like a star in the right situation. Noel is only 23. He still has time to find it.