Tom Thibodeau, Julius Randle and RJ Barrett discussed the Knicks' victory after they held the Cavaliers to 79 points in a dominant Game 3 to take a 2-1 lead in the best-of-7 series on Friday. Credit: Newsday/William Perlman

Donovan Mitchell was 16 years old the last time the Knicks were able to fill Madison Square Garden to capacity for a playoff game, a matchup he attended when he was young enough not to remember all of the details other than the noise. So he knew what to expect when the Cleveland Cavaliers and the Knicks took the floor Friday night.

“Chaos.”

And the chaos that he had predicted after the morning shootaround arrived, but probably not the way he expected. As soon as the Cavaliers won the opening tip, the raucous Garden crowd erupted into a loud chorus of “de-fense!” chants. And in the din of a crammed arena, the Knicks delivered.

Whether it was a throwback to the Knicks teams that once thrilled the crowds at the Garden with hard-nosed defense, the floor-rattling noise of the crowd or simply a night of brick-throwing by Cleveland, the Knicks dominated Game 3, 99-79.

“It’s the Garden, man,” RJ Barrett said. “What can I say? It was loud and fun to play in, man. As a basketball player, you grow up thinking about moments like these. It was electric in the air, and glad we get to come back Sunday.”

The 79 points represented the lowest output by any team this season. The Cavaliers’ previous low was 81, also at the Garden.

Asked if the Cavs were shook by all of this, Mitchell Robinson said, “I’m not them. But probably.”

The win gave the Knicks a 2-1 lead in the best-of-seven first-round playoff series with just a short breather before Game 4 at the Garden at 1 p.m. Sunday.

The Knicks got 21 points and six assists from Jalen Brunson in his first Garden playoff game and 19 points and eight rebounds from Barrett, who joined the series after a sluggish first two games. And what the Knicks got most of all was a defensive performance — even when their best perimeter defender, Quentin Grimes, was lost for the second half with a contused right shoulder — that brought back memories of the franchise’s glory days.

Tom Thibodeau was able to empty the bench with 3:46 to play, leaving only chants of “Derrick Rose!” to be answered from the crowd. With 2:30 left, the call was answered and the roof seemed ready to blast off of the Garden. A Rose-to-Obi Toppin lob for a dunk gave the crowd one more reason to celebrate before streaming for the exits.

“Being in this environment, there is no replica,” Brunson said. “There is nothing that comes close to it. And I’m just happy to be a part of it.”

Mitchell had 22 points and Caris LeVert added 17. Darius Garland, who had 32 points in Game 2, shot 4-for-21 and scored 10 points.

The Cavs — and not just Mitchell, who grew up in Westchester County — spoke of the history of the Garden and the expectations for a playoff game here. But as the Knicks noted in returning home after the split in Cleveland, the crowd would help only if the Knicks gave them something to cheer about.

Maybe it’s his New York upbringing, but Mitchell seemed to know what was coming. “It’s the first time in 10 years it’s been full capacity, right?” he said. “I told the guys just be ready for it. It’s gonna be exciting. It’s gonna be fun. It’s gonna be a dogfight. We sent a statement in Game 2, and you expect them to respond. That’s their character. That’s their makeup as a group.”

When no one else seemed up to the task early, Barrett got the Knicks started with 10 points and five rebounds in the first quarter. He shot 4-for-6 in the quarter, but the rest of the Knicks shot a combined 2-for-17, including 0-for-9 from beyond the arc. But Barrett’s effort was enough for the Knicks to manage a 17-17 tie after one quarter as Cleveland also struggled, including an 0-for-8 quarter from Garland.

The Knicks returned home aware that they would need help from someone other than Brunson and Randle. Barrett was a likely candidate after shooting 6-for-25 in the first two games. He had started seven postseason games entering Friday, five against Atlanta two years ago and the two in Cleveland. In that span, he shot 34.7% from the field and 25.0% from three-point range.

Cleveland’s struggles continued as the Knicks held them to 32 points — a season low for a half — and built a 13-point lead heading into halftime.

“It’s one game is what it is,” Thibodeau said. “Now the challenge is get ready for Game 4. So we gotta take a look at the film, look at the things we could do better, make our corrections and then be ready for the game on Sunday. But I think the activity on defense was important for us. They missed some open shots, too, so we know the next challenge will be even greater, and we gotta play better.”

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