For many teams, the 2021 NBA offseason could be a time of subtle change.

Kawhi Leonard is the only superstar free agent, and it seems highly unlikely he will leave the Los Angeles Clippers. That's, perhaps, just as well, since few teams have major money to spend and even fewer pair significant cap space with win-now attentions.

But for a handful of clubs, the coming months could bring about radical transformations.

Whether because of playoff disappointments, roster flaws or, in one case, a superstar's exit that spawned a top-to-bottom overhaul, the following five teams might enter next season in completely different shape than they exited this one.

Boston Celtics

So much for summer vacation.

The Boston Celtics have already kept plenty busy since their five-game, first-round series loss to the Brooklyn Nets. Former president of basketball operations Danny Ainge retired, and former coach Brad Stevens stepped into that spot. Barely two weeks into his new role, Stevens authored a blockbuster, sending Kemba Walker and draft picks to the Oklahoma City Thunder for a package built around former Celtic Al Horford.

This could be only the beginning for a team that fell woefully short of expectations this season. The Celtics were supposed to contend for the crown; they went .500, had to punch their playoff ticket in the play-in tournament and were knocked out of the opening round.

Jayson Tatum is going nowhere. He's the organizational centerpiece. Jaylen Brown is probably staying put, too, though if the Portland Trail Blazers are ready to talk Damian Lillard trades (more on that later), Brown could conceivably top their wish list.

If the Celtics swing a big trade without sacrificing a star wing, that probably means the end of the road for their longest tenured player, Marcus Smart. It could also mean giving up a prospect or two such as Romeo Langford, Aaron Nesmith or Payton Pritchard to sweeten the offer and up the return.

Boston doesn't have much of consequence heading to free agency beyond deadline acquisition Evan Fournier. The Celtics presumably want to keep him for his support scoring, shooting and table-setting (and have more future financial flexibility after the Walker deal), but if an offense-starved shopper blows up his market, he could be out of the equation, too.

Dallas Mavericks

The Dallas Mavericks are nearly two months away from being able to rework their roster, and they are already unrecognizable.

Rick Carlisle, their head coach since 2008, is gone. His exit was preceded by the departure of president of basketball operations Donnie Nelson, who spent the past 23 years with the franchise. Nelson's farewell followed a report from The Athletic's Tim Cato and Sam Amick detailing such disorder within the front office that it has caused concern about Luka Doncic's desire to stay long-term.

Other than that, though, things are fine. Or wait, no, they are absolutely not.

The Mavericks have not only failed to find their coveted third star, they also just watched presumed second star Kristaps Porzingis flop in their first-round series loss to the Los Angeles Clippers. Over the seven games, he netted 20 points once, finished in single digits three times and encountered myriad issues with defensive mobility. His future earnings ($65.5 million over the next two seasons) and injury history hang a massive cloud over the organization.

Dallas will almost certainly shop Porzingis this summer, but the Mavs may not like the market they find. It's hard to imagine they will net more than a similarly imperfect, high-priced player or maybe a collection of non-stars.

Dallas could have more than $35 million in cap space this summer—flexibility that will be gone going forward once Doncic inks his max extension—but it would cost the team a rotation regular such as Tim Hardaway Jr., Josh Richardson or Willie Cauley-Stein.

The reshuffling has already started, and it could spiral over the coming months.

Houston Rockets

In the past calendar year, the Houston Rockets have traded James Harden, Russell Westbrook, Victor Oladipo, Robert Covington and P.J. Tucker. The resulting roster could lead to an entire round of "Who He Play For?" on TNT.

Because Houston is in such an early state of its rebuild, it employs a smattering of relatively interesting youth and a lot of placeholders. That will probably still be the case next season, though the place-holding portion of the team could include a lot of new faces since the Rockets have just six players with guaranteed contracts for 2021-22.

Of that group, only two appear as automatic keepers: Christian Wood and Kevin Porter Jr. Once the Rockets guarantee the contracts of Jae'Sean Tate and Kenyon Martin Jr., they'll enter the circle of trust, too, but that's barely a rough outline for Space City's 2021-22 iteration.

On the trade front, Houston seems likely to shop Eric Gordon, Danuel House Jr. and D.J. Augustin to win-now buyers. The Rockets will surely try to pawn John Wall, too, but given his injury history and future earnings ($44.3 million next season and a $47.4 million player option for 2022-23), his tenure with the team will more likely end via a buyout.

It's perhaps worth noting general manager Rafael Stone stressed a desire to field a competitive roster at his end-of-season news conference. While that sounds like something you might say to not alienate a fanbase that could still be reeling from The Beard's departure, maybe there's a scenario in which the Rockets are actually buyers this offseason. We wouldn't go about it that way, but it's not our call to make.

Either way, the 2021-22 Rockets could look dramatically different than their 2020-21 version.

Portland Trail Blazers

It isn't always easy for NBA teams to determine their formulas are flawed, but two things should force the Portland Trail Blazers to make that concession.

First, this club has been knocked out of the first round in four of the last five postseasons. Optimists will note there was a Western Conference Finals appearance in there, but pessimists will point out Portland merely had to beat an Oklahoma City Thunder squad that reset itself after that season and a young Denver Nuggets club that was still learning how to win.

Perhaps that's not enough alone to force the front office into action. But Damian Lillard's message after the Blazers were bounced by a Nuggets team missing its starting backcourt should be.

"Obviously where we are isn't good enough to win a championship if it's not good enough to get out of a first-round series with two of their best three or four players not on the floor," Lillard told reporters.

The Blazers have since split from Terry Stotts, their coach since 2012. Starting center Jusuf Nurkic wondered aloud if he would return. Lillard and his backcourt mate CJ McCollum have become regulars on the trade-machine circuit. Norman Powell (player option), Carmelo Anthony and the intriguing-but-often-injured Zach Collins (restricted) lead a sizable group of Portland's impending free agents.

And while Portland has no 2021 draft picks to put in a trade, Anfernee Simons and Nassir Little loom as possible sweeteners.

Lillard will turn 31 in July. If he's not running out of patience with the status quo, Portland's decision-makers should be.

Washington Wizards

If you listen closely, you can probably hear the collective groan of the Washington Wizards fanbase. Yes, folks, we are here to talk about the potential Bradley Beal trade that he and the team keep saying won't happen.

But what, exactly, is Washington supposed to be chasing?

The Wizards can't fashion themselves as title contenders. They weren't a .500 team this season, needed to win a play-in tournament game just to make the playoffs and were forcibly removed from the postseason with their last three losses coming by a total of 71 points.

Next season, they'll have $94.7 million tied up between Beal, Russell Westbrook and Davis Bertans, but the rest of their roster is filled with unproven youth. It's like they have one eye on the present and the other on the future. Again, what's the focus?

More importantly, what should it be?

"The right move is to [trade] Beal and probably buy out Westbrook," an Eastern Conference executive told Sports Illustrated's Howard Beck.

The Wizards seem unlikely to go that far during the offseason, if only because what they can get for Beal now (while surely still massive) might lag behind what they could have fetched at the trade deadline. But they have already split from coach Scott Brooks and may continue to make not-insignificant changes.

Robin Lopez, Ish Smith, Raul Neto, Garrison Mathews (restricted) and Alex Len will be free agents, and outside of maybe Mathews, they all look like flight risks. If the Wizards aim to compete and bring a decent chunk of these players back, then they should probably package some of the prospects and draft picks (including this year's 15th selection) for players more capable of helping Beal and Westbrook right now.

Still, external calls for Washington to pull the plug won't go away until it takes the plunge or substantially improves the roster around its backcourt. That's a busy offseason either way.

Stats courtesy of NBA.com and Basketball Reference unless otherwise noted. Salary information via Spotrac.

Zach Buckley covers the NBA for Bleacher Report. Follow him on Twitter, @ZachBuckleyNBA.