This disappoints me, and I assume it disappoints NBA fans, as well.

Kevin Durant signs a two-year contract with the Golden State Warriors.

Happy Fourth of July, hoops fans!

Durant was a free agent, and could join any team he chose.

He hosted presentations in the Hamptons, an upscale region near New York City, and the Los Angeles Clippers, San Antonio Spurs, Boston Celtics and Miami Heat flew to NY and made their cases — as did the Warriors and the Oklahoma City Thunder, the only franchise for which Durant had played.

And Durant chose the least entertaining option, the one that leaves the NBA a less competitive league — while offering him his best chance at an NBA championship.

The Warriors. Giving Golden State four of the 12 best players, in the reckoning of Bill Simmons, NBA honk and historian.

In Oakland, Durant joins Stephen Curry, Draymond Green and Klay Thompson, and the latter three just led the Warriors to a record 73 victories and to a Game 7 defeat — to LeBron James and the Cleveland Cavaliers — in the NBA Finals.

More specifics on why this is bad for the league:

–The list of teams who have a realistic chance of winning the league has declined to three — the Cavaliers out of the less competitive Eastern Conference, the Warriors and, being a bit generous, let’s include the San Antonio Spurs.

The Thunder? Taking Durant off that team and adding him to the club that beat OKC in the West finals … well, the Thunder and solo star Russell Westbrook are not winning the next NBA title. Neither are the Clippers.

–Durant just answered one of the interesting competitive questions in the league: No, he cannot lead the Thunder to an NBA title. And you would think that would hurt the competitor inside Kevin Durant. Remember, OKC led the Warriors 3-1 in games in the West finals before losing the final three. Wouldn’t that make him want to stay? Or at least go somewhere else than into the camp of your arch-rivals?

We should not frame this in financial terms. Durant will be paid $54 million over a two-year deal, with a player option to become a free agent after the first season. However long he stays, he could have made about $4 million extra per season by remaining in OKC, which could offer him more money over more years.

Plus, he is going to have to pay the California state income tax, and Durant will be in the top bracket of that tax — handing over 13.3 percent of his income (about $3.6 million per season), and that’s before the feds come along with their hands out. (FYI: Florida and Texas have no state income tax, and the Heat and Spurs play in those two states. So, no, this is not about salary.)

In addition, we do not really know if the move makes financial sense on the marketing and personal-endorsement side. What does it mean for his shoe deal? Who knows.

No, this should be seen in competitive terms.

One of the league’s great players would rather join forces with a bunch of the other great players and win a title the easy way — or easier, anyway.

I am disappointed that Durant did not want to stay in OKC or join some other team — one that hadn’t just won 73 games — to see if he could take down the Warriors.

I am disappointed that he apparently is not competitive enough to want to win a championship with his team rather than becoming one of two-time MVP Stephen Curry’s sidekicks. An illustrious sidekick, to be sure, but the Warriors are Curry’s team.

This clustering of stars in a handful of NBA teams is not healthy for the league. Fans of 26, 27 NBA teams are kidding themselves if they look in the mirror and say, “This is going to be our year!”

This clustering of in-their-prime players began with Kevin Garnett and Ray Allen joining Paul Pierce with the Celtics, in 2007. They won the 2008 title.

It picked up momentum when LeBron James jumped from the Cavaliers to the Heat in 2010. He joined Dwyane Wade and Chris Bosh, and the Heat won the Eastern Conference four consecutive seasons, with two titles, in 2012 and 2013.

And now this. Perhaps the most distressing move yet, in terms of what it means for fans of the league.

It isn’t just me. ESPN.com is doing a survey of fans, and 61 percent of more than 330,000 respondents believe Durant’s decision is the wrong one. Forty-five percent believe he should have stayed with OKC; 16 percent believe he should have gone elsewhere; 39 percent believe the Warriors were the right move for Durant.

Yes, the NBA season is long, and people can get hurt. Curry has that wonky ankle, and his knee was a problem in the playoffs. Durant has a screw in his foot.

But if they stay reasonably healthy … not even LeBron deciding to stay in Cleveland (and he also is a free agent) is likely to make enough of a difference to stop the Warriors.

Has any of America’s big-four sports leagues approached a season with so few legitimate contenders? I think not.

I am disappointed … and also bored.