So much for finally breaking through last year. So much for basically putting the Celtics on the brink even before Jayson Tatum tore his Achilles in Game 4 of the second round, for beating Boston in their first playoff matchup since 2013, for — despite their inability to beat the Celtics consistently during the regular season — signaling the potential for a changing of the guard atop the Eastern Conference. Maybe Boston was still Boston, but the Knicks could do more than just hang.

But so much can change in a year. Tatum is already back from an injury that typically sidelines athletes for a year. He returned in just 298 days. The Celtics have leapfrogged the Knicks in the conference standings and will likely end up as the No. 2 seed, too. And the Knicks have been plagued by rocky stretches and an inability to defeat teams above .500. The decision to fire Tom Thibodeau and hire Mike Brown has paid off at times, but key pieces such as Karl-Anthony Towns and Mikal Bridges have still been inconsistent — and sometimes invisible.

The Knicks convincingly winning their Eastern Conference semifinals series last year was supposed to vault them to a new tier. But instead, they almost need to beat the Celtics again to establish themselves as a true contender and silence any critics suggesting otherwise. Because until then, the optics suggest that the Knicks are still chasing the Celtics.

Entering the season, this had been pegged as a rebuilding year for Boston. Sure, they still had Jaylen Brown. Sure, they still had Derrick White. But, with an increasingly onerous payroll, they sent Kristaps Porziņģis to the Hawks and shipped Jrue Holiday to the Trail Blazers. The Celtics, like the Pacers without Tyrese Haliburton, were supposed to be outside the tier of contenders. That was supposed to open the door for the Knicks. If there was any year where they’d have a clear path to at least reach the NBA Finals, this was going to be that year.

CLEVELAND — Brick by brick, the Knicks were dismantled by the Cavs.

An atrocious shooting night ended Tuesday with a 109-94 loss for New York, which folded easily to its fellow Finals contender and left Rocket Arena tied for third in the East.

The third quarter was the breaking point. Or better yet, bricking point. It was horrendous.

The Knicks managed just 11 points in those 12 nasty minutes, shooting a combined (shield your eyes, children) 3-for-24 overall, 1-for-12 from beyond the arc and 4-for-8 from the foul line.

So they entered the fourth quarter down 18 and couldn’t recover, not against a stout Cavaliers defense and without the help of competent shooting.

Mike Brown finally waved the white flag with 2:42 remaining, emptying his bench and sending the starters to the walk of shame.

Mikal Bridges, Josh Hart, Jalen Brunson, Landry Shamet and OG Anunoby combined to miss 42 of their 61 attempts. Bridges was aggressively misfiring at 6-for-17 on the evening.

Brunson was worse at 6 for 19. Karl-Anthony Towns was perfect but only took five shots, furthering the head-scratching trend of alternating strong performances with disappearing acts. Anunoby (five points, 2-for-9 from the field) has struggled since returning from a toe injury.

Brown’s attempt to give an opportunity to Jeremy Sochan was also a miscalculation, with the newcomer appearing utterly lost in his two first-half minutes. Mohamed Diawara got the call in the second half and also tossed up bricks.

It was an all-around dud. The Cavs responded with a balanced but not especially potent attack. They shot just 42.5 percent as a team but it didn’t matter against the Brickerbockers.

The Knicks (37-22) are now even with the Cavs (37-22) and at least 1 ½ games behind the No. 2 Celtics, who played Tuesday night against the Suns.

But the Cavs are surging. They revamped at the trade deadline, acquiring James Harden for the talented but habitually unavailable Darius Garland. They also brought in bench pieces Dennis Schroder and Keon Ellis.

It’s all been positive for Cleveland, which has won 13 of 15 after Tuesday’s blowout. Kenny Atkinson just missed out on guiding Harden in Brooklyn before he was unceremoniously dumped by GM Sean Marks and owner Joe Tsai. Now he’s excited for the chance in Cleveland.

“His composure, calmness,” Atkinson said. “He’s just got a command of the game. That settles everybody down. It’s huge. He knows where the ball’s got to go. He knows the end of game stuff. Sharp, sharp player.”

The Knicks understood the difficulties of defending Harden and Donovan Mitchell, perhaps the best offensive backcourt in the NBA.

But defending wasn’t the problem Tuesday for the Knicks. It was the bricklaying.

“You know how tough Harden is,” Bridges said. “His ability to create, not just for himself, but for everybody else at really an elite level. They’ve got a tandem with Donovan, how well he’s been playing and everybody else. Can definitely be tough.”