It’s a sad day in San Antonio – and an exciting one for other teams, starting with the Lakers – with Kawhi Leonard and the Spurs looking like they’re past the point of no return.

The Spurs trail the Warriors 3-0 in their first-round mismatch, one loss from the offseason with Kawhi nowhere in sight.

Rather than sitting on the bench to lend his teammates support, he’s in New York with his new medical team … which has been no more successful in getting him over the mysterious thigh injury that kept him out for all but nine games this season.

That cheering you hear is the parade cranking up in Lakerdom. Byron Scott, who is close to Magic Johnson, actually announced on ESPN, “I’m going to tell you something right now. LeBron (James) is coming to the Lakers along with Kawhi. We’re back in the Finals!”

Reports dovetailing with that one swept the league:

Kawhi, a Los Angeles guy who grew up in the Inland Empire, wants to come home.

Kawhi, who has one year left on his contract, will force a trade to the Lakers.

Of course, the teams can’t discuss it – especially the Lakers after incurring two tampering penalties this season, an NBA record, which could get them barred from bidding if they breathe wrong.

That makes this the kind of story everyone loves best, with lots of star players on the move that can be molded to fit any need with no one dealing with the sticking point:

Why would the Spurs trade the 26-year-old Leonard to their ancient rivals, the Lakers?

It says here they won’t.

• With a year left on his contract, the Spurs must sign off on anything Kawhi does this summer.

With less to offer in trade than other teams, the Lakers need him to force a deal, which he might well try, and for the Spurs to accede, which is less likely.

Playing one more season for the Spurs would give Leonard all the leverage – but he and the Spurs might be past that after Kawhi trashed his “selfless” image and bailed on the team.

Waiting a year won’t work for the Lakers, who need a second star to persuade LeBron to come. If they can’t get Kawhi this summer, they might go back to their original dream package with Paul George and LeBron.

• It’s one of Popovich’s cardinal rules not to help Western Conference rivals, much less one with the tradition and resources of the Lakers.

Popovich almost never says a bad word about another team, but he went bonkers in 2008 when Memphis traded Pau Gasol to the post-Shaquille O’Neal Lakers, setting them up for three consecutive Finals runs and two titles.

“What they did in Memphis is beyond comprehension,” Popovich said at the time. “… I just wish I had been on a trade committee that oversees NBA trades. I’d like to elect myself to that committee. I would have voted no to the L.A. trade.”

• We’ll never know if Popovich might deal with the Lakers if all things are equal. All things aren’t.

Several contenders – such as the Celtics, 76ers and Cavaliers – have more young players and/or high first-round picks to offer the Spurs.

The Lakers have Brandon Ingram, Lonzo Ball, Julius Randle and Kyle Kuzma – all promising young players but none yet a star Popovich could build around. They don’t have their own first-round pick – now an unprotected No. 10 – which finally goes to Phladelphia (a pick the 76ers could, of course, offer the Spurs.) The Lakers’ No. 25 pick would mean little to San Antonio.

And, of course, the Celtics, 76ers and Cavaliers are in the Eastern Conference, Popovich’s preferred destination for Leonard, if not Kawhi’s.

The Clippers must be just as interested as the Lakers, but all they have is an aging roster and the No. 12 and 13 picks. (Drawing a top-three pick in the lottery could change things, but there’s just a 4.7 percent chance of that happening.)

Of course, for Popovich, this is the nightmare scenario that he never imagined after the extraordinary run that saw a tiny market team win as many titles as the Lakers (five) from the Spurs’ first in 1999 to their last in 2014. Other teams expressed their admiration by hiring half the people who once sat next to Pop on the bench or worked in their front office.

As opposed to the zany Lakers, who saw the Shaq-Kobe champions break themselves up, the Spurs ran on auto-pilot with Tim Duncan providing in-group leadership until his 2016 retirement.

The summer before Duncan called it quits, the Spurs signed LaMarcus Aldridge, a gifted player but, as far as greatness, a flawed one, known for telling friends on other teams to get him over there as the weight of responsibility presses on his shoulders … as it did by his second season in San Antonio when he asked to be traded.

“I was very candid with him,” Popovich said later. “I told him I would be happy to trade him. ‘You get me a talent like Kevin Durant and I will drive you to the airport. … Short of that, I’m your best buddy and you are here for another year and you ain’t going nowhere because for you talent-wise, we are not going to get what we want (in a trade) so let’s figure this thing out.’

“And we did.”

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Adam Silver says he talked with LeBron James, Kawhi Leonard about Lakers’, Clippers’ choice to play on Unfortunately, as it turned out, Aldridge wasn’t the biggest problem they had.

Indignity piles atop indignity. The Washington Post just ran a piece headlined, “Insulted pro-Trump Spurs fans feel forced to choose between their team and the president.”

“I often curse Pop for doing what he did (criticizing Trump),” Bob Mulherin, a longtime fan told the Post. “He insulted more than half of the Spurs’ fan base and no sign whatsoever of an apology.”

Of course, this is sports and all about winning … or what you have done for anyone recently … as opposed to politics. Popovich first criticized President Trump in the fall of 2016. It didn’t become an issue last season when the Spurs were still elite.

Nothing is forever, not even the Spurs, the Spurs just learned.

Mark Heisler has written an NBA column since 1991 and was honored with the Naismith Hall of Fame’s Curt Gowdy Award in 2006. His column is published weekly during the NBA season with the Southern California News Group.