That was so uncool.

New Knicks enforcer Marcus Morris said the club would protect its home court this season, promising, “No one’s coming in there and disrespecting us.”

That’s exactly what happened. The Knicks were “disrespected’’ on their home floor by the woeful Wizards in Friday’s home preseason opener, a 115-99 rout.

They were outclassed by Wizards star shooting guard Bradley Beal, who pumped in 21 first-half points as the Wizards built a 65-47 halftime lead.

The Knicks’ only star Friday was its crowd. The Knicks sold out their preseason home opener.

Chanting “de-fense’’ in the final quarter as the Knicks mounted a charge, the Garden has miraculously stayed mostly packed amid a depressing six-year playoff drought. But even they booed the club in the final seconds.

When the Knicks last left the Garden court six months ago, 115-89 losers to the Pistons in their season finale, there was belief the 17-65 club would return armed with two new stars and a playoff roster.

Instead, the Knicks returned Friday with a roster of role players after a $70 million spending spree.

Their highest-paid signee, Julius Randle, who signed for three years, $63 million, was poor in the first half, notching five points and four turnovers. He finished with 14 points and five turnovers.

Starting point guard Elfrid Payton, who looked so smooth in the preseason opener, was 0 for 9 with two turnovers — a minus-24. Mitchell Robinson was in foul trouble all night, committing five in 10:47.

It is hard in a preseason game to give up 17 straight points and allow a 31-6 run, especially to potentially the league’s worst team. The new Knicks turned the trick and got blitzed 41-17 in the second quarter.

“We stopped defending the 3,’’ Knicks coach David Fizdale said. “We relaxed. Going from game one to two, our closeouts were a nightmare.’’

In the nightmarish second period, Fizdale’s bunch allowed the Wizards to shoot a breezy 8 of 12 from the 3-point line, 15 of 23 overall. Sounds a lot like last season.

All that camp talk about stepping up the pressure defense this year looked foolish, as the Wizards pumped in wide-open launches from all over Manhattan. Even more bizarre, the Knicks once held a 30-15 edge after early Morris and RJ Barrett surges before they completely collapsed in a 50-17 onslaught.

“We kind of relaxed,’’ Randle said.

Somewhere not in China, Kevin Durant is definitely limping — and probably smiling. Friday figured to be Durant’s Garden debut as many “done-deal’’ observers thought in April.

Instead, the Knicks unveiled their deep-to-the-15th-man team, heavy on the front line and bragging about an old-school 1990’s Knicks’ toughness.

Fizdale, with former Detroit enforcer Ben Wallace at Thursday’s practice and Friday’s game as GM Scott Perry’s guest, has invoked the 2004 championship Pistons.

There was nothing tough or remotely playoff-worthy Friday. Getting thumped by the woeful Wizards is alarming, even in preseason.

Durant already has disrespected the Garden without even showing up. His comment about the Knicks brand not being “cool’’ any longer was a sucker punch to president Steve Mills and Fizdale, who have run a campaign to improve the club’s image.

“It’s like the cool thing right now is not the Knicks,” Durant said on the radio.

Durant’s use of the word “cool’’ is suspect until the Nets show they can fill their Brooklyn digs. The Nets finished 42-40 last season — and last in the league in attendance. That’s not so cool.

The Knicks have been losers for years, but, incredibly, they have not lost their mammoth fan base. Maybe this will be the year that finally changes if the Nets rise up some more and the Knicks turn into a 20-win laughingstock, back to Chicago with solid odds at the lottery.