Milwaukee Bucks forward Giannis Antetokounmpo and Philadelphia 76ers center Joel Embiid have made waves in recent weeks by suggesting that they might open to moving on from their current teams.

Their comments speak to the inherent challenges of building a team around a superstar in the NBA.

During an interview at the Uninterrupted Film Festival in mid-July, Embiid told Maverick Carter that he wanted do whatever it takes to win a championship, whether "in Philly or anywhere else." Antetokounmpo recently echoed that sentiment to Tania Ganguli of the New York Times NYT .

"At the end of the day, I feel like all my teammates know and the organization knows that I want to win a championship," he said. "As long as we’re on the same page with that and you show me and we go together to win a championship, I’m all for it. The moment I feel like, 'Oh, yeah, we’re trying to rebuild'… There will never be hard feelings with the Milwaukee Bucks."

Antetokounmpo still has two guaranteed years left on his contract before a $51.9 million player option for the 2025-26 season, while Embiid has three guaranteed years left before a $59.0 million player option in 2026-27. Neither star intimated that they're imminently poised to request a trade like Bradley Beal, Damian Lillard and James Harden did this offseason.

However, they're understandably concerned about the long-term outlook of their respective teams. Such is life when you have to maximize a win-now window around a superstar.

Both the Bucks and Sixers have made all-in pushes in recent years to optimize their championship odds with Antetokounmpo and Embiid. In November 2020, the Bucks traded Eric Bledsoe, three future first-round picks and two first-round pick swaps in a four-team deal to acquire Jrue Holiday. Antetokounpo signed his five-year, $228.2 million supermax extension one month later, and the Bucks proceeded to win the NBA championship that season.

The Sixers have not been as fortunate, albeit not for a lack of trying. They've acquired Jimmy Butler, Tobias Harris and Harden via trade over the past half-decade, although they still have yet to make it past the Eastern Conference Semifinals with Embiid in the fold. A confluence of poor decision-making and injury misfortune has repeatedly caused them to fall short of advancing past the second round of the playoffs.

As both stars approach their 30th birthday—Embiid turns 30 in March, while Antetokounmpo will in December 2024—they might be coming to grips with their basketball mortality. A player typically reaches his athletic prime in the latter half of his 20s, but it only tends to last for a few years. After that begins a slow and steady decline, during which they'll eventually no longer be able to carry a team to a championship.

The Bucks' acquisition of Holiday already paid off with one ring, but their long-term outlook is far murkier. The 33-year-old Holiday revealed earlier this year that he plans to retire from the NBA at the conclusion of his contract in 2024-25, while Brook Lopez (35) and Khris Middleton (32) are also on the wrong side of 30. Unless MarJon Beauchamp or A.J. Green take a major leap in the coming years, the Bucks are short on young, high-upside players once their current core ages out.

The Sixers are slightly better off in that regard thanks to 22-year-old guard Tyrese Maxey, the No. 21 pick of the 2020 NBA draft. After playing sparingly as a rookie, Ben Simmons' holdout forced him into the starting lineup ahead of the 2021-22 season, and he's fresh off a year in which he averaged a career-high 20.3 points per game on 48.1 percent shooting.

Team president Daryl Morey routinely admits that Maxey has already surpassed the Sixers' expectations. He believes the Kentucky product has All-Star ability, and he expects Maxey to be a cornerstone of the team moving forward. (They're only holding off on extending him because of what Morey called a "quirk" of the collective bargaining agreement.)

The Sixers also have high hopes for fourth-year big man Paul Reed, whose three-year, $23.6 million offer sheet they matched this summer in restricted free agency. Reed told Ky Carlin of Sixers Wire that new head coach Nick Nurse has talked about molding him into a "Pascal Siakam-type player," someone who can "kind of do it all."

Maxey and Reed are promising building blocks, and 25-year-old two-way guard De'Anthony Melton could fit that mold as well if the Sixers re-sign him next summer in free agency. But unless third-year guard Jaden Springer takes a leap this coming season, the Sixers are also largely devoid of other high-upside developmental prospects, which could have Embiid eventually eyeing an exit.

Because of previous transactions, both teams are short on future first-round picks to either spend on young prospects or use in trades for win-now players. The New Orleans Pelicans have the right to swap first-round picks with the Bucks in 2024 and 2026, while the Bucks will send their 2025 first-rounder to either New Orleans or the New York Knicks and their 2027 first-rounder to the Pelicans, all courtesy of the Holiday trade. They've also traded away all of their second-round picks through 2030 except for their 2027 second-rounder.

The Sixers, meanwhile, owe a top-six-protected 2025 first-round pick to the Oklahoma City Thunder and a top-eight-protected 2027 first-round pick to the Brooklyn Nets. They forfeited their 2024 second-rounder as part of the punishment for tampering with P.J. Tucker and Danuel House Jr. ahead of free agency last summer, and they've already traded away their 2025 and 2026 second-rounders as well.

The NBA's new collective bargaining agreement could further restrict both teams' ability to retool around their respective stars. The Bucks are already $6.5 million above the new second salary-cap apron, which prevented them from having access to the taxpayer mid-level exception in free agency this offseason. They'll be subject to a host of additional restrictions if they stay above that level next summer.

Mindful of those new limitations, the Sixers are angling to create as much salary-cap space as possible next summer. However, there's no guarantee that they'll be able to land one of the biggest fish in the free-agent pond such as Siakam, Kawhi Leonard or Paul George—or that those players will even become free agents in the first place.

These team-building tensions are a sign that the CBA is working as intended. It's hard enough to assemble a championship-caliber roster in the first place, but it's even more difficult to sustain that level over time. The San Antonio Spurs are the only team to have successfully done so in the past two decades, and that required two generational stars (Leonard and Tim Duncan), one of the greatest coaches in NBA history (Gregg Popovich) and happened under far less restricted CBAs.

Whenever you go all-in, the bill eventually becomes due. The Boston Celtics had an incredible five-year run at the end of the 2000s after acquiring Kevin Garnett and Ray Allen, but they eventually had to trade Garnett and Paul Pierce and begin anew. The Portland Trail Blazers are on the precipice of that now with Lillard.

The days of a superstar playing his entire career for one team may be over. At a certain point, it's often better for both team and player to part ways. The player has a better chance of pursuing a championship elsewhere, and the haul that his incumbent team receives in return can help expedite their rebuild.

If the Bucks and Sixers part ways with Antetokounmpo and/or Embiid in the next few years, it won't necessarily be because their respective organizations failed them. It'll just be the natural life cycle of NBA team-building at work.

Unless otherwise noted, all stats via NBA.com, PBPStats, Cleaning the Glass or Basketball Reference. All salary information via Spotrac or RealGM. All odds via FanDuel Sportsbook.