NEW YORK — All season long, the Cleveland Cavaliers made their bones on the defensive end of the court, topping the charts in points allowed per possession and holding 29 opponents under 100 points — by far the most of any team in the NBA.

The Cavs made it an even 30 on Friday night, holding the Knicks to just 99 points in Game 3 of their opening-round series and limiting New York to a rate of offensive efficiency (106.5 points per 100 possessions) that would’ve ranked dead last in the NBA during the regular season.

And yet: The Cavs lost by 20, thanks to one of the most dismal offensive displays you’re going to see in a playoff game.

Friday’s 99-79 beatdown marked the Cavs’ first 20-point loss of the season, and their lowest-scoring game of the season; in fact, it’s the first time in all of the 2022-23 campaign that any team in the NBA scored fewer than 80 in a game. Cleveland’s previous low-water mark for the season? An 81-point outing against … the Knicks, back on Dec. 4, in the first game after Tom Thibodeau tightened his rotation.

That December blowout sparked a run that would transform the Knicks from an under-.500 also-ran into one of the league’s best squads over the next four months, sending them on their way to 48 wins, the East’s No. 5 seed and a date with Cleveland in Round 1. This latest one gives New York a 2-1 lead in their best-of-seven series, the chance to seize control with another win in Game 4 on Sunday and newfound confidence that — so long as they don’t beat themselves — they can dictate the terms of engagement to the higher-seeded Cavaliers.

“We did what we needed to do,” Knicks All-Star Julius Randle said after a disruptive effort that saw New York rack up 14 steals, five blocked shots and 12 deflections. “I feel like we’ve been playing well all series on the defensive end. Only thing that hurts us, really, is our turnovers. We had a lot of turnovers in the second quarter last game. So we cleaned that up, and we was able to get stops and execute.”

The Cavs seemed rattled and might have overthought some things

Cleveland, on the other hand, played perhaps its messiest and worst-executed game of the season, at a pretty awful time for it.

Before the game, coach J.B. Bickerstaff fielded questions about Madison Square Garden — about whether he felt this building was a little bit different come the playoffs and about whether he had any concern that young charges like Game 2 hero Darius Garland and Evan Mobley might quake a bit while playing their first road playoff game in The World’s Most Famous Arena.

“I think if you allow the outside noise to overflow into the floor, you can overthink it, right?” Bickerstaff said. “At the end of the day, our message to our guys is, no matter what, it’s five-on-five basketball, and if you focus on the work that's in front of you, none of the other stuff that's outside the lines matters. … If you allow those things to be a distraction, they can impact you. But if you just go out and do the job that's in front of you, you'll be fine.”

The Cavs couldn’t do the job Friday, though. They came out of the gate shooting 8-for-24 with four turnovers in the first quarter — a rocky start Bickerstaff later attributed in part to nerves — and never fully got on track. After his brilliant Game 2, Garland had the most miserable night of his young career; despite being guarded primarily by frequent mismatch target Jalen Brunson, Garland missed his first nine shots, entering halftime with just three points and finishing with a whisper-quiet 10 points on 4-of-21 shooting.

Garland’s nightmare was most glaring, but he was hardly the only Cavalier to disappoint. The frontcourt of Jarrett Allen and Evan Mobley once again struggled with New York’s physicality, as Mitchell Robinson bulldozed his way to the front of the rim for five offensive rebounds, blocked two shots and snagged two steals in the paint on the other end, and partnered with Randle and backup center Isaiah Hartenstein to present an imposing enough impediment at the rim that — to hear him tell it — the Cavs decided they didn’t much feel like venturing inside anymore:

Outside of Mitchell (a team-high 22 points) and LeVert (who scored all 17 of his points after halftime), the Cavs absolutely could not buy a bucket for most of the game. As Mitchell succinctly summed it up: “We shot like crap.”

The failures extended beyond the shooting, though. The Cavs largely abandoned success they found with targeting Brunson on offense and switched Brunson’s ball screens far more often than they did in Game 2, only returning to the more successful strategy of blitzing him in the second half, after he’d already found his scoring and playmaking rhythm. Ricky Rubio briefly reappeared in the rotation; Isaac Okoro, benched after the opening minutes of Game 2, got dusted off for seven minutes in the second and third quarters, during which Cleveland got outscored by 10 points.

It felt a little bit like the Cavs, in preparation for adjustments they felt the Knicks would make coming out of Game 2, tweaked things on their own in a fashion that might have been too clever by half …

… which, combined with the rancid shooting on all manner of looks, doomed them.

The young Knicks finally showed up

While Garland and Mobley stumbled coming off strong performances in Game 2, New York’s prized prospects found steady footing. R.J. Barrett bounced back with a solid outing, scoring 19 points with eight rebounds, three assists and a steal. He attacked from the opening tip, looking to drive on the smaller Garland when the two were matched up, to turn the corner on handoffs and staggered screens to search for paint touches and to seize opportunities to sprint the floor in transition off defensive rebounds or turnovers (of which Cleveland committed 20, leading to 28 Knicks points).

“The thing about R.J. is, he’s very steady,” Thibodeau said after the game. “He doesn’t get rattled. I thought he was real aggressive today. We’ve got to get him into the open floor. When we do that, he’s going to make shots, he gets downhill, and he's tough to guard.”

After shooting just 6-for-25 in Cleveland, Barrett went 8-of-12 from the floor and made three triples in six tries. Asked after the game when he felt like he’d gotten his shot online, Barrett asked a Knicks communications staffer what day it was; upon being told it was Friday, he replied, “OK, so Wednesday.”

After scoring just three points in Game 1 and only getting going after Game 2 was well out of hand, Immanuel Quickley flashed the form that made him a Sixth Man of the Year finalist, chipping in 11 points, a pair of assists and stout defense in 23 minutes — during which the Knicks outscored Cleveland by 27 points.

Jalen Brunson got free with a little help from his friends

Quickley also played a role in helping Brunson get back into a groove after a 5-of-17 performance in Game 2. Quickley set seven ball screens for Brunson on Friday, according to Second Spectrum, joining Josh Hart (11 screens), Barrett (six screens) and Quentin Grimes (two screens before leaving the game with a left shoulder contusion) in the project of trying to force Cleveland’s guards to switch onto Brunson in the pick-and-roll.

“I feel like they made that adjustment and it was really good for them,” LeVert said after the game. “That’s definitely something that we can communicate better. I’ve got to do a better job of listening up top to the coverage and making sure I’m sending him in the right direction.”

Those guard-guard screens allowed him to attack whichever wing defender he preferred — Mitchell, Garland, LeVert, Cedi Osman, whomever — without fear of the long-limbed Mobley and Allen lurking on the other side of the screen, waiting to trap him at the point of attack. They worked: After a 1-of-5 first quarter, Brunson got into the flow, alternating between hunting his own shot in isolation and drawing help before kicking to a teammate ready to either catch and shoot or catch and drive:

Once Brunson got going, the floodgates opened. He’d finish with 21 points on 10-of-18 shooting with six assists, leading the dance and getting the Knicks off to the races.

“Just letting the game come to me,” Brunson said after the game. “I’ve got to trust my teammates. They have the utmost confidence in me, and I’ve got the utmost confidence in them. We’re all on the same page. We’re all clicking.”

If they’re able to keep clicking come Sunday, the Cavs could find themselves heading back to Cleveland staring down elimination, with regrets over opportunities — and a bushel full of jump shots — missed.