The Garden opens for Knicks business Friday with their first preseason home game against the Wizards. The arena may burst with noise because it has stayed mostly full amid the depressing six-year playoff drought.

When the Knicks last left the Garden court six months ago, 115-89 losers to the Pistons on April 10, there was belief the club would return in the fall armed with two new stars and a playoff roster.

Friday will not mark Kevin Durant’s Garden debut as many “done-deal’’ observers thought in April. Actually, Durant would not have played Friday even if he had joined the Knicks. What is not cool for the Nets is Durant will likely miss all four regular-season matches against the Knicks as he rehabs from an Achilles tear.

Instead, on Friday, the Knicks will finally unveil their deep-to-the-15th-man team, heavy on the front line and bragging about an old-school toughness. Maybe it will be the toughness from 1990s Knicks or the toughness from GM Scott Perry’s old Pistons clubs led by Ben Wallace, a visitor to their Tarrytown headquarters Thursday.

Either way, the new assemblage could be pretty cool — in theory. However, when the Knicks opened the preseason Monday in Washington, the display that led to Marcus Morris’ ejection was not basketball toughness. Bopping Wizards forward Justin Anderson in the head with the ball, after nearly clocking him with a swinging elbow, was childish.

Morris is lucky the NBA didn’t suspend him for the regular-season opener, but the league probably has too much on its mind with the controversy in China. Morris, who likes to remind everyone he’s from North Philly, will have to tweak his act a notch.

New Knicks big man Bobby Portis should make his debut Friday after missing the preseason opener with sore ribs. He’s got a history, too, after punching out one of his Bulls teammates, Nikola Mirotic, during a practice in 2017.

Morris and Portis need to use their aggression the right way and maybe the Garden can be something cool this season. Morris said during training camp the Knicks need to “protect the Garden.”

“My biggest thing is no one’s coming in there and disrespecting us,” Morris said.

Durant has already 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 head coach David Fizdale, who have run a campaign to improve the club’s image.

“These younger players, in their lifetime, don’t remember the Knicks being good. … So that whole brand of the Knicks to them is not as cool as, let’s say, the Golden State Warriors or even the Lakers or the Nets now,” Durant said during a radio interview this week on Hot 97.

“It’s like the cool thing right now is not the Knicks.”

Durant echoed a comment TNT’s Kenny Smith made to The Post last weekend. The congenial Smith, who talks to a lot of players, opined: “There has to be re-education to certain players about the Knicks that they are the biggest stage. There’s certain players who grew up not knowing Patrick Ewing played for the Knicks. There’s a generation of players that don’t understand the magnitude of what being a Knick is.”

Smith’s point is well-taken. However, Durant’s use of the word “cool’’ is suspect. All he needs to say is he wanted to win and the 17-65 Knicks looked too far away.

But the Knicks not being cool? Durant said he, Kyrie and DeAndre Jordan wanted Brooklyn because of the team’s recent success. 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 and the Garden has not lost its buzz. The Knicks were ninth in attendance last season at 19,002.

Maybe Durant is searching for excuses. The truth could be he’s concerned about facing the biggest microscope amid the challenge of returning from basketball’s most devastating injury. LeBron James admitted to confidants in 2010 he was wary of his family’s privacy if he became a Knick.

Former Knicks coach Jeff Van Gundy alluded Thursday to Durant shying away from the blinding glare for the smaller lens of Brooklyn.

“I don’t think ‘on Broadway’ is for everybody,’’ Van Gundy said on ESPN. “Off Broadway is for some. On Broadway is for some. New York is certainly not for everyone. It’s for special players. I do believe all it takes is one great player like Patrick Ewing or Stephen Curry, the right, best player to come to the Knicks franchise, and they will once again be cool. There is no place to play like New York City.”

And it starts Friday night with a bunch of hungry new Knicks role players adamant about proving Durant’s “cool’’ remark wrong.