All it took was one-and-a-half home games for the Knicks to hear their first boos of the season. Unless they find a way to stop teams, those boos will rain down more often and louder, and the team Phil Jackson built will have another disappointing season.

The Knicks gave much less-than-maximum effort on the defensive end for the second straight game, and James Harden and the Rockets completely took advantage of it.

The Rockets scored 100 points through three quarters and rolled to a 118-99 win over the Knicks at Madison Square Garden. This was the most points the Knicks (1-3) have allowed this season. Jeff Hornacek’s team also allowed 117 and hasn’t yielded less than 100 in a game yet.

“If we don’t come out and play defense we’re going to keep getting smacked like this,” Derrick Rose said.

Harden just schooled the Knicks with his playmaking and shooting. A perfect player for Mike D’Antoni’s system, Harden finished with 31 points and 15 assists. Harden was 9-for-15 from the field, and knocked down five three-pointers, a few of them were the step-back variety.

How easily everything came for Harden drew some ire from the normally mild-mannered Hornacek. He said the Knicks aren’t aggressive enough and need to show more pride.

“It’s almost like we let James do whatever he wanted,” Hornacek said. “We had breakdowns. Coaches work hard to put scouting reports in and we got to make sure we follow them.”

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Carmelo Anthony led the Knicks with 21 points. Rose and Courtney Lee each had 16, but Kristaps Porzingis was invisible. He had no impact, no field goals and scored just three points.

But the defense remains the Knicks’ biggest issue. The boos started late in the first half after the Knicks fell behind 68-48, and picked up again late in the third. Trying to spark something, Hornacek tried some different and even unimaginable things.

In the third quarter, he took out former Defensive Player of the Year Joakim Noah and replaced him with undrafted rookie guard Ron Baker.

Hornacek went small, hoping the Knicks could make some stops, force turnovers and get back in the game. The Knicks scored on two straight possessions to get within 14, but the good feelings quickly faded.

Harden scored the last eight points of the third quarter to give the Rockets a 100-78 lead.

“We just lost really badly,” Noah said. “It easy to come in here and say I want to play more. That’s not what it’s about. We got pounded on the glass by 20. That has nothing to do with the coach. That’s us coming in here with the right intensity and having the will to fight.”

The Knicks, who lost in Detroit Tuesday, can’t use the excuse that they were tired from completing a back-to-back. The Rockets lost in Cleveland Tuesday, and still had enough energy to nearly match the 120 points they scored against the Cavaliers.

Eric Gordon added 21 points for the Rockets, Montrezl Harrell 17 and Ryan Anderson 16.

“It’s not like we haven’t done defense in practice,” Hornacek said. “Our guys are offensive minded guys. We have to do be able to do it on both ends. But again the defense has been taught and preached and practiced.

“Sometimes it comes down to taking it upon yourself to stop somebody and not look for help. You have to have more fight one-on-one defensively.”

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After the Detroit loss, Rose said the Knicks need to forge an identity, and invoked the name Tom Thibodeau, who brought defense and toughness to the Bulls.

Rose said he wants the Knicks to be known as “Just a hard-working team. Just know it’s going to be a battle every night or time you come into this arena and whenever you play us. It’s about building a culture and it takes time for that.”

He said it takes about 20-25 games to develop an identity. Hornacek said the Knicks’ should be “a team that goes out there and plays hard all 48 minutes.”

Right now, the Knicks’ identity is what it has been for many years: a team that won’t put up much resistance on the defensive end.