NEW YORK — The Knicks blew the game open in the second quarter. But 76ers coach Doc Rivers could foresee the onslaught percolating in the opening 12 minutes.

The Sixers shot poorly (29% from three-point distance), committed 15 turnovers leading to 19 New York points and allowed far too many open looks in a 112-99 loss to the Knicks Tuesday night at Madison Square Garden that was easily the Sixers’ worst performance of the early season.

Rivers was most irked with how his team failed to combat New York’s physicality, which disrupted flow on both ends of the floor of a game they trailed by as many as 27 points.

“That was as bad as I’ve seen us, and I didn’t like it,” Rivers said. “We’ll get it fixed. ... Get open. Own your space. I mean, that’s what you do. We had guys leaning backwards, leaning away. It was unbelievable to watch. How many times did you see us leaning away from the basket, falling away? Guards, bigs, everybody. You cannot allow someone to be in your space.”

It was a night Rivers said “nobody played well,” despite star forward Tobias Harris narrowly missing a triple-double with 23 points, nine rebounds and nine assists. MVP contender Joel Embiid (14 points, 6 rebounds, 3 assists) attempted only seven shots (though he went 10-of-11 from the foul line), prompting him to text his trainer after the game to ask if he was being too passive. Second-year guard Tyrese Maxey remains a work in progress when it comes to playing the point.

Overall, the ball movement was poor and the defense did not tighten up enough to create transition opportunities.

The Sixers are now 2-2, with their two wins against inferior opponents and the two losses to teams expected to be in the thick of the Eastern Conference playoff picture. The Sixers return to the Wells Fargo Center for a four-game homestand, beginning Thursday against Detroit.

Clunky start

The first quarter may have foreshadowed the second-quarter collapse for Rivers. But things fell apart in the final seven minutes before halftime, when the Knicks staged a 20-6 run to turn a clunky-yet-competitive game into a blowout. Immanuel Quickley got the onslaught started — and ignited the home crowd — when he put on a move that sent former college teammate Maxey to the floor before burying a three-pointer.

The Knicks outscored the Sixers 39-16 in the decisive second quarter, paced by a blistering 6-of-7 mark from three-point distance during that frame. The Sixers were 0-for-5 from beyond the arc in the period.

Neither team shot well from the floor in the first quarter, with the Sixers going 8-of-22 and the Knicks going 7-of-22. The Sixers built a three-point lead by generating free-throw attempts (8-of-9) and taking care of the ball (one turnover). But Rivers called that opening frame “fool’s gold.”

Those positives dissipated in the second quarter. The Sixers turned the ball over eight times in the period, leading to 11 Knicks points. They shot only four free throws. And while the Knicks snapped out of their offensive slump, the Sixers never found their rhythm.

Embiid, meanwhile, missed all five of his shot attempts in the first half. He continues to suffer from soreness after getting knocked knee-to-knee in last week’s opener, but said “it’s not an excuse” for his performance. He continues to look for the ideal balance of being a dominant force and getting teammates involved as a “point center.”

“I wasn’t aggressive enough,” Embiid said. “Not even close to what I should be. … I don’t think I’ve played like this to start off the season or [in] any stretch of my career.”

Rotation tightens

After playing a 10-man rotation in each of the first three games, second-year guard Isaiah Joe was largely the odd man out Tuesday. Maxey and Seth Curry both got first-quarter breaks but returned later in the frame, while Furkan Korkmaz also manned backcourt minutes. Joe eventually entered in the third quarter’s final minute and played in the fourth, when the game was out of hand.

Rivers had typically started the second and fourth quarters with an all-bench unit. Tuesday, Maxey was on the floor with Korkmaz, Matisse Thybulle, Georges Niang and Andre Drummond.

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After a terrific preseason, Joe had not made a shot in the regular season until he made one of four three-point tries Tuesday.

Niang was the second unit’s leading scorer with 13 points, though 11 of those came in the largely inconsequential second half. Drummond, who returned from a one-game absence due to a sprained ankle, finishied with 6 points, 9 rebounds, and 2 assists. Korkmaz missed his first five shots and finished with nine points on 3-of-12 from the floor.

‘Where’s Ben Simmons?’

The Sixers have played three of their first four games on the road. But after facing subdued crowds in New Orleans and Oklahoma City, the Garden was revved up.

During the second quarter, an upper-deck section started a “Where’s Ben Simmons?” chant that began to spread throughout the arena and could be heard on the TNT broadcast. The chant resurfaced with about five minutes to play in the game, and then again as fans left The Garden.

A similar (but less boisterous) chant began during last week’s opener at New Orleans, along with a “We want Ben!” chant.