USA Basketball’s senior men’s team is losing steam at an alarming rate. In the past few weeks, the roster expected to defend the United States’ FIBA World Cup championship this summer in China lost its two biggest stars, Anthony Davis and James Harden, and two key shooters in Eric Gordon and C.J. McCollum.

The churn continued this week. Just before this piece was published, Bradley Beal withdrew due to the impending birth of his child. After this piece was published, Damian Lillard — expected to be the star of the team — pulled out, as did Philadelphia’s Tobias Harris. Zion Williamson, who was unlikely to play anyway, also made it official that he would sit. Several other players from the original roster, including Kevin Love and Paul Millsap, have also pulled out.

Former FIBA stars like LeBron James, Kevin Durant, Stephen Curry, Kawhi Leonard, Russell Westbrook, Klay Thompson, Draymond Green, DeMarcus Cousins, Blake Griffin, Paul George, and Kyrie Irving were already out for various reasons.

In fact, of the 11 Americans on the All-NBA team this past season, only one is currently slated to participate in the World Cup: Kemba Walker. There were 20 NBA All-Stars this season who are eligible for USA Basketball service. Only three remain on the roster: Walker, Khris Middleton, and NBA champion Kyle Lowry, who had thumb surgery after the season and might not be back in time.

Here’s what the depth chart looks like going into camp after the recent pull-outs.

Guards: Walker, Donovan Mitchell, Lowry, Marcus Smart

Wings: Middleton, Jayson Tatum, Jaylen Brown, Harrison Barnes, P.J. Tucker.

Bigs: Andre Drummond, Myles Turner, Kyle Kuzma, Brook Lopez, Thaddeus Young, Julius Randle, Mason Plumlee

Keep in mind that five years ago, Lillard was cut from a World Cup roster because Team USA had so many stars. (The player that got Lillard’s spot? Derrick Rose. Welp.) How times have changed, for Lillard and especially for USA Basketball. His late withdrawal opens a glaring hole on the roster.

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There’s no good answer for why this is happening. The senior men’s team has its best coach ever in Gregg Popovich. Steve Kerr and Lloyd Pierce are assistant coaches. The opportunity to spend a couple of months with that coaching staff, both stateside and overseas, sounds like a dream. Contrary to popular belief, the World Cup actually is important even though American fans don’t pay much attention: the clearest way to qualify for the 2020 Tokyo Olympics tournament is to finish top two among Western Hemisphere teams in the World Cup.

Now, Team USA is still talented enough to easily finish top two among the seven North American, South American, and Caribbean teams (Canada, Brazil, Argentina, Puerto Rico, Venezuela, United States, and Dominican Republic). Most of those teams have also suffered some attrition due to retirements, NBA commitments, and injuries. And if something wild happens and the United States really falls apart, there’s a last-chance tournament before the Olympics next summer, at which point the stars could come out and clinch a spot fairly easily, one would imagine.

In fact, the United States is still the overwhelming favorite to win the World Cup, even with this stripped-down roster. The senior men’s team hasn’t lost a tournament game since 2006, when the U.S. finished third under Mike Kyrzyzewski in the reboot tournament after the embarrassment of the Athens Olympics in 2004. Serbia and Spain are Team USA’s biggest rivals for the title, and since Giannis Antetokounmpo has announced he will play for Greece, you can’t count out the team that beat the Americans in 2006. But yes, USA Basketball is the huge favorite, even without Harden, Davis, Lillard, and everyone else.

The question here is, why they are without everyone else.

There’s no security or health issue keeping stars away, as there was in Athens 2004 (terrorism threats) or Brazil 2016 (Zika virus). The host nation is China, still NBA stars’ favorite foreign market to pitch. Popovich is well-liked and known to more NBA stars than Coach K had been. There hasn’t been a major injury suffered in international tournament play or preparation since 2014, and that didn’t seem to have a huge impact on the 2016 Olympic roster.

Is it complacency? As mentioned, the Americans haven’t lost in a tournament in more than a decade. Wounded pride sparked American NBA stars to participate beginning in 2006. There’s no wounded pride on the world basketball stage at this point. Is that a necessary component to getting a higher level of commitment from the best players?

Is it a lack of pre-existing friend groups and cliques? From 2006 through 2012, the senior men’s team was defined by the LeBron-Wade-Melo-Bosh crew. Around 2014, we saw the sprouting of the Kevin Durant-Kyrie Irving friendship that rocked this summer’s NBA free agency. Walker and Middleton are off the market. Mitchell and Tatum are on rookie deals. None of these players seem all that connected together. It’s a pretty random group.

Is it pressure from teams? There hasn’t been any public suggestion of that. It’s possible that given the enormous contracts being doled out these days, there has been behind-the-scenes requests by teams to skip the summer. Or, perhaps players are doing the math themselves.

Is it politics? Is the allure of proudly wearing U-S-A across your chest less appealing now than in, say, the years 2008 through 2016? That might be true, though 2006’s high level of star participation sticks out, and the presence of Popovich and Kerr should calm fears of being misunderstood on the world stage.

Is it the fact that USA Basketball has not stuck to its guns on requiring stars to eat their vegetables (playing in the FIBA World Cup, which most American fans and merch buyers don’t care about) to get their dessert (playing in the Olympics, which tons of Americans watch and love)?

Is it the timing of the tournament at the end of the NBA offseason? The World Cup championship game is Sept. 15. There are preseason games the first week of October.

It’s likely some combination of these factors, personalized for each star player.

But whatever the case, this is easily the weakest Team USA has been heading into a major tournament since 2004 (maybe even 2002, when the Americans finished sixth as a host nation) and it’s exactly what Jerry Colangelo and the leadership of USA Basketball has worked to avoid over the past 15 years.

Kemba, Pop, and the others will probably still cover the United States in basketball glory. But it won’t be as easy as it could have been, and it’s worth figuring out why it’s heading back in this direction.