For three quarters, Kyrie Irving and Joel Embiid redrew the world in their own images.

Irving executed a pick-and-roll clinic, strapping defenders onto his back and firing off floaters and acrobatic layups a split-second before help arrived. He dove into the paint, faked and hit impossible faders.

Embiid dominated in the post, straddling to the left and to the right, sinking hook shots, finessing up-and-unders and drilling short jumpers. He treated double-teams from the Celtics’ smaller perimeter guards like a man who understood his station relative to theirs, leveraging his 7-foot, 250-pound frame to split through the defense and land at the basket. When burlier forwards like Jaylen Brown approached, he fired away from the perimeter. It felt like a natural extension of his desire to be more bruiser than floor spacer, until he sunk two threes without hesitation.

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Al Horford, his primary defender, stymied Embiid and nearly played him off the floor when the Celtics minced Philadelphia in five playoff games last May. The Celtics sagged off Ben Simmons, the jumper-less Rookie of the Year, and crowded the paint, making the starting lineup that dominated last year’s regular season look outmoded and inflexible. Nearly every decision Philadelphia has made since then has been with an eye toward becoming a team suited for playoff dominance. And it appeared the revamped Sixers, 13-7 since trading two-fifths of that lineup for four-time All-Star Jimmy Butler, were turning over a new leaf.

But then the fourth quarter hit, and Embiid and the 76ers came crashing down to Kyrie’s flat earth. The Celtics turned up the pressure, ignored Simmons and sagged off Butler just so, finding more agreeable spots to trap Embiid, suffocating him and forcing the 76ers to cough up nineteen turnovers and a deluge of late-clock shots.

“I felt like I could have done more,” Embiid told reporters after the 121-114 overtime loss Tuesday. “I didn’t get the ball. The ball didn’t find me in the fourth and in overtime. In those situations, I gotta show up, but then also I gotta be put in the right situations to help the team, and I felt like I wasn’t in the right situations.”

Indeed, Embiid accumulated 28 of his 32 points in the first three quarters. When asked if he thinks opponents regularly make effective second-half adjustments against him, he implied that double-teams shouldn’t deter his teammates from feeding him the ball. “Doesn’t matter,” he said. “I think everybody knows I’m a willing passer, that I’m not selfish. I’m gonna get guys involved. It doesn’t matter if they send a double- or triple-team, which I see a lot.”

In the meantime, Kyrie Irving’s crunch-time exploits became even more fantastical. Surrounded by floor-spacers, Irving isolated on Butler, drove into the paint and unfurled an off-dribble turnaround fadeaway that left his fingertips, narrowly escaped Butler’s outstretched arms, plopped through the net and sent the game to overtime. In overtime, Irving — who rarely ever has to wait for a solid post-entry pass before making his move — caught the ball on a dribble-handoff and immediately rose for the three that gave Boston their definitive lead. On the next possession, he sprinted up the floor in transition and nailed another heat-check triple, powering Boston’s 13-1 run to close out the game.

For the 76ers, Irving’s performance was damning not only because of what he did to them, but because it was a reflection of what they haven’t done: maximize the talent of their best player at the end of close games.

“In that environment,” Brown told reporters after the game, “all I think about it is: 92-92, three minutes left, Game 6. What are you going to do? And if that were the case tonight, we’d be in trouble. The good news is it’s December the 25th and this conversation can’t be had in late April, early May. We’ve got lots to work on. This will be a great reference point for me.”

One wonders: What can really change between now and then? Butler, an elite scorer whose 39 percent stroke is only sullied by his low volume, certainly rounds out a Big Three better than Fultz. And the departures of Dario Saric and Robert Covington in the Butler deal made way for JJ Redick to re-enter the starting lineup.

But the core structural problem persists: three All-Stars who don’t space the floor well surrounded only by two potential floor-spacers at a time, diminishing all of their strengths.

In the post, Embiid finds himself walled off on an island, contested jumpers and awry passing angles his only option. Putting Simmons in the post neutralizes his inability to shoot and lets him leverage his generational passing chops, but it turns Embiid into a glorified spot-up shooter. Butler, an excellent cutter and driver, is often aided by Simmons’ vision only to find himself stymied by a help defender. Simmons thrives in transition; Embiid plods behind. All the while Butler is inclined to fill the same lanes they do.

In these moments, the reductive nature of the discourse around Simmons’ inability to shoot makes sense. Why focus on the one glaring flaw in a 6-foot-10 wonder with the vision to manifest passing lanes where none existed, turn the game into a layup line with a head of steam, post up and switch multiple positions on defense? Because pressure reduces the game to its core elements: In the closest thing to a playoff environment the 76ers have faced since being knocked out by the Celtics in May, the best they played was when Embiid played without Simmons and Butler.

Brown and the 76ers understand that they’re working against the math. In fact, they’ve always respected the math. The Process was almost disturbingly analytical, which makes it all the more baffling that they’re now trying to win a championship with a core of below-average shooters. How is it that the Sixers, who headed the most meticulously planned rebuild in NBA history, look like an accident?

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