There's no such thing as an untradable NBA player. It's just that some—due to contract, health, declining production or a combination of all three—are a little harder to move than others.

You know the guys we're talking about. They're the ones rival executives won't even take calls on unless the player in question's current team is ready to pile on sweeteners in the form of valuable contracts, draft assets or both.

The "well, actually..." crowd will note that most of the players we'll cover have been traded in the past—some of them recently. Two were even dealt for each other. But in each case, things have changed since the last time those players switched teams. New problems have arisen that complicate the prospect of another exchange, even as the costly deals they're on draw closer to expiration.

Nobody's saying these players are stuck where they're at until whenever free agency mercifully rolls around. But figuring out how to move them before that will be among their teams' most important and challenging goals.

Tobias Harris, Philadelphia 76ers

For most of the past eight seasons, Tobias Harris has been a reliably healthy and productive offensive player. He's averaged 74.4 games played since 2014-15, the year he became a full-time starter for the Orlando Magic. And in every year since assuming that role, he's graded out as above average at his position in points per shot attempt.

Better still, he's shown growth in the past half-decade, hitting over 39.0 percent of his threes in three of the last five seasons after failing to reach that mark in any of his first six years in the league.

So what's the problem? What's he doing on this list?

Cost is the main issue. Harris signed a five-year, $180 million extension with the Philadelphia 76ers in the 2019 offseason and is still owed $37.6 million in 2022-23 and $39.2 million the following season, all fully guaranteed. That's superstar money for a player who, while talented offensively, has long failed to justify his high-end salary with game-changing impact. In 2021-22, Harris was a flat 0.0 in Dunks and Threes' Estimated Plus-Minus. His career high in that catch-all stat was the plus-2.2 he managed in 2020-21, which ranked 62nd in the league among qualified players.

Despite a career that shows he's barely been a break-even contributor (at his best), Harris is currently in line to be the league's 13th-highest-paid player in 2022-23.

The Philadelphia 76ers won't be able to trade him without attaching a young talent like Tyrese Maxey or draft considerations. Even then, they'll still need to find a team with ample cap space to absorb Harris' hefty deal or, perhaps less palatably, take back someone else's unwanted overpay.

Duncan Robinson, Miami Heat

For two glorious seasons, Duncan Robinson did one thing better than almost anyone. And that one thing, shooting high-volume threes on the move, happens to be worth a ton.

So the Miami Heat gave him a five-year deal worth $90 million in August 2021. It made sense at the time. Shooting is the NBA's premium skill and Robinson, for those two years, was elite at it. Across the 2019-20 and 2020-21 seasons, the undrafted forward shot 42.7 percent from deep, by far the highest accuracy rate of anyone who got up at least 900 treys.

Robinson suffered some slippage in 2021-22, the first year of his new deal, as his three-point percentage dipped to 37.2 percent. Meanwhile, another undrafted scrap-heap find, Max Strus, shot 41.0 percent on a minimum deal and eventually seized Robinson's starting job. Worse still, Robinson's role all but disappeared in the playoffs.

In a hypothetical trade negotiation, the Heat could make the pitch that Robinson's disappointing season still featured above-average three-point shooting, and that the larger sample of the prior two years should carry at least as much predictive value as 2021-22. It's hard to imagine Robinson's accuracy won't trend back north of 40.0 percent. But good luck to Miami when it tries to justify Robinson's price tag so soon after it replaced him with a similar player making as little as the league allows.

At $16.9 million next season (ascending to $19.9 million by 2025-26), Robinson's deal isn't a cap killer. But the downside risk attached to a one-skill player is daunting. If Robinson doesn't rediscover his shot, he won't be able to provide value in any other way. There's a non-zero chance he becomes an end-of-bench player making a starter's salary.

Ben Simmons, Brooklyn Nets

The best realistic case for any team acquiring Ben Simmons is that the three-time All-Star will fully recover following back surgery and perform exactly like the guy who averaged 14.3 points, 7.2 rebounds and 6.9 assists and made the All-Defensive first team in 2020-21.

Even then, Simmons' conspicuous habit of shrinking from the biggest moments will hang over him. The stain of the 2021 playoffs, which saw Simmons attempt zero shots in the last four fourth quarters he played against the Atlanta Hawks, may never wash out.

There are darker timelines.

Simmons' back trouble may persist, sapping athleticism and mobility from a player who needs tons of both to compensate for his shooting limitations. His season-long struggles with mental health may not be behind him either, which could further compromise his availability.

And don't expect new teammates to trust Simmons right away, if ever. Toward the end of his tenure, the Sixers with whom he shared a locker room were skeptical about his commitment.

The obvious counter is that Simmons was traded just a few months ago, so it could certainly happen again. But the swap that sent him to the Brooklyn Nets in exchange for James Harden was unusual. Both stars had asked out, and their teams had few alternatives. Now, Simmons carries all the same questions he did prior to joining the Nets, plus the stigma of back surgery. That's a ton of uncertainty to take on at a cost of $113.7 million over the next three seasons.

John Wall, Houston Rockets

John Wall didn't play at all last year and has appeared in just 40 games since 2018. A player whose success depended largely on elite physical talent, namely speed, Wall does not profile as someone who'll retain much effectiveness on the other side of a layoff that long.

Remember, prior to last year's season-long excused absence from the Houston Rockets, injuries were already taking their toll. Wall played only 41 games in 2017-18 and 32 in 2018-19.

At $47.4 million next season (player option), Wall will surely be among the most overpaid players in the league—and that'd be true if he somehow suited up for all 82 contests, an impossibility given his track record.

It made sense when the Rockets and Los Angeles Lakers discussed swapping their unwanted and expensive point guards, as B/R's Jake Fischer reported in April. Our problem for yours, basically.

But no deal materialized, and it's not like there's a glut of fallback options on the market. That Westbrook and Wall were already traded for one another in 2020 is pretty good proof of that.

If you can't trade those two for each other, you can't trade them at all.

Expect Houston to buy out the final year of Wall's contract in July, sending him into free agency where he'll suddenly become an intriguing low-cost option for a contender. That'll serve as a good reminder that being untradable isn't the fault of any of these players. The blame belongs on the franchises that offered (or traded for) their albatross deals in the first place.

Russell Westbrook, Los Angeles Lakers

Forget the money, even if $47 million is a ton of cash to try to wipe from your memory. The greater obstacle to trading Russell Westbrook is the former MVP's failure to adapt as he's aged.

Uncompromising competitiveness has always been among Westbrook's greatest gifts. You can imagine how a franchise that employed Kobe Bryant for 20 seasons would admire that characteristic. But Russ' indomitable will doomed the deal that brought him to the Los Angeles Lakers as a theoretical third star alongside LeBron James and Anthony Davis.

Westbrook's 2021-22 was the worst season of his career as measured by win shares and Box Plus/Minus. His undisciplined defense and wayward shooting, though unsurprising, stung more because his waning athleticism meant there was no compensating for those shortcomings with relentless rim attacks. The fit was bad from the start, but Westbrook's diminishing skills and stubborn refusal to change his game mean switching locations won't make things any better.

He's already past the point where he can run past or jump over the competition.

When a former star plays for a different organization in four straight seasons, it's a pretty good indication that the issue is with him, not the surrounding circumstances.

New Lakers head coach Darvin Ham praised Westbrook in his introductory press conference, but he also laid out a set of expectations that involved ego subjugation and defensive accountability—the same ones deposed coach Frank Vogel did.

The Athletic's Bill Oram noted the echoes and their uninspiring implications: "How did Westbrook respond to Vogel’s overtures of sacrifice? By ignoring Vogel’s pleas to sacrifice and throwing him under the bus within hours of him officially being fired."

If the Lakers manage to trade Westbrook, they'll only accomplish it by finding the foolhardy team that thinks it can change him...and throwing in every draft pick they're allowed to part with as payment for the hassle.

Stats courtesy of NBA.com, Basketball Reference and Cleaning the Glass. Accurate through 2021-22 season. Salary info via Spotrac.