Kristaps Porzingis had no problem getting open shots and knocking them down in the Knicks’ first preseason game Tuesday night. The Rockets had an even easier time.

New coach Jeff Hornacek said there is “no need to panic” after the Knicks played defense like it was a pick-up game and put up no resistance in a 130-103 loss in Houston.

Hornacek chalked up the numerous breakdowns to how the Rockets play and that he hasn’t put in any defensive schemes. He didn’t necessarily give the Knicks a defensive game plan Tuesday. Hornacek wanted to see how the Knicks played, helped and communicated. Simply put, not well.

He’s using this as a barometer for what the Knicks need to improve upon before the regular-season opener Oct. 25 at Cleveland.

“We got to play a little tougher,” Hornacek said. “[We need] a little more physical play on the ball. I think we were kind of playing it too safe. Being a little more physical playing a guy one-on-one, and then weak-side help.”

James Harden excelled at his new position as point guard in Houston’s fast-paced, wide-open offense under former Knicks coach Mike D’Antoni. Harden had 28 points and 11 assists. He frequently set up Ryan Anderson, who hit seven of Houston’s 20 three-pointers. Many of them were uncontested.

Former Defensive Player of the Year Joakim Noah was unable to play due to a sore hamstring. His presence would have made a difference, but Hornacek said the Knicks can’t rely on one player.

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“We have to be known for our defense when we come into the regular season,” Derrick Rose said. “We don’t want it to be easy. We’ve got to go out there and just play as hard as we can, compete and let teams know that they’re not going to walk all over us.”

Defense should be a focal point of their next practice Thursday, but Rose won’t be there. He flew to Los Angeles on Wednesday for his civil sexual assault trial. It’s unclear when he will return.

Offensively, the Knicks struggled initially before finding a rhythm. They scored 61 points in the second half. Porzingis played well on that end of the court, going 5-for-6 on three-pointers with 22 points total.

Porzingis, who shot 4-for-4 on three-pointers in the third, was the beneficiary of Rose penetrating and getting the defensive attention, as well as Brandon Jennings.

“They created quite a lot of shots for me,” Porzingis said. “It’s great playing alongside those guys. They’re so quick, creating opportunities for us, for me to shoot wide open. The only thing is I have to make those shots.”

Rose, in his Knicks debut, was able to get to his spots and create for himself and his teammates. He had 16 points and five assists. But Rose harped on the lack of defense.

“I’m more worried about our defense than anything,” Rose said. “We’re going to score the ball. I’m not worried about that. We have to be that team defensively where when we come in you know you’re going to have a hard night on that side of the ball.”