Coach Joe Mazzulla and the Celtics hope to regain control of the series vs. the 76ers in Game 3.

PHILADELPHIA – From all appearances — on the sideline and at the podium — Joe Mazzulla, coach of the Boston Celtics, has all the charm and charisma of his in-market counterpart: New England Patriots coach Bill Belichick.

No smiles, little apparent enjoyment, tolerating the tedium of engaging with reporters as if getting instructions on an upcoming colonoscopy. The NBA’s revised dress code would even let him wear a hoodie at the Boston bench if he wanted.

There’s absolutely nothing wrong with any of that, not given the results Mazzulla has achieved in his rookie season guiding the Celtics. They went 57-25 in the regular season, the franchise’s most successful since 2008-09 and six games better than a season ago under terminated predecessor Ime Udoka. They are positioned well for a repeat turn in the NBA Finals, and remain the favorites of oddsmakers to win the 2023 NBA championship.

So Mazzulla was well within his rights when he ended his postgame media session after Game 2 Wednesday night, in the minutes after Boston’s 121-87 drubbing of the Philadelphia 76ers, by rhetorically spiking his clipboard on his audience.

Remember, the Celtics coach had been backed into a corner after Game 1, most pointedly about sticking with switching single-coverage of James Harden as the Sixers’ scorer danced into a 3-point shot with 8.4 seconds left that lifted them to a 119-115 victory. “The Beard” already had blistered Boston for 42 points as that play unspooled, and when 2022 Kia Defensive Player of the Year Marcus Smart switched onto scoreless P.J. Tucker out of the pick-and-roll, veteran big man Al Horford was left to defend Harden by his lonesome.

That’s what they do, Mazzulla said. That’s how they play. Horford has shown the ability to guard on the perimeter. Hindsight is easy. And so on.

So 48 hours later, after a 34-point blowout that set the Celtics’ world straight, Mazzulla answered all the inquiries in his flat, terse, mostly expressionless way. At the end, he dropped one on the reporters.

“Nobody wants to ask about all the adjustments we made from Game 1 to Game 2?” he asked, getting up and walking out. As he exited the room, he said quietly to a Boston friendly, “They didn’t like that.”

Fact is, Mazzulla was right and he was wrong. He didn’t get a specific question about X&O tweaks from the rattling loss to the emboldening triumph. But there were obvious reasons beyond failing to give a still-learning NBA coach his due.

First, postgame interrogations are just that: Post game. By nature, they are hindsight. Folks know Mazzulla’s preferred brand of defense, but in such an exceptional moment it was worth asking about a possible exception.

Second, the difference in circumstances from Game 1 to Game 2 was so dramatic — NBA MVP Joel Embiid was back for Philadelphia after missing the opener — that Boston’s game plan required an overhaul, not mere adjustments. Had the Celtics again been taking on an Embiid-less crew, then a close look at the two or three changes that flipped embarrassment into success might have been warranted.

For instance, Boston sub Grant Williams played four insignificant minutes in the first game. In the second? Williams logged 29, poked Philadelphia with four 3-pointers and hounded Embiid defensively. That was dictated by the Sixers center’s return, not a film-session brainstorm.

Finally, the Celtics’ biggest adjustment had been evident, both during the game and in the questions and answers of Mazzulla’s 10-minute podium visit: They played angry. They played frustrated. They played harder.

That last one is the first rule of playoff basketball. It’s been on display since this Eastern Conference semifinals series began. The Sixers played harder Monday because they were desperate, lacking their best player in a hostile building. The Celtics seized that edge Wednesday because of getting caught flat-footed, maybe assuming themselves what so many fans and other observers — oops! — had expected to happen.

To a man, from Jaylen Brown to Malcolm Brogdon to Horford, Williams and Smart, they all emphasized how much they dialed up their intensity and concentration. Sometimes it’s not intricate coaching at all.

Later, after learning of Mazzulla’s remark, Smart said: “I’m not surprised he asked you guys that, but I’m proud of him. We expect to be perfect sometimes. And we forget this is his first year in this spot with the reins, and he’s doing a phenomenal job at it. But we’ve got to relax and let him learn as well. He understands, he has his staff there, they’re talking, and they’re going to make the right adjustments.”

Game 3 is on the clock now for Mazzulla, Sixers coach Doc Rivers, their respective staffs and all their players. While short of mandatory, a victory Friday night at Wells Fargo Center — after Embiid receives the Michael Jordan MVP Trophy before the home fans — could be pivotal for either side.

A Celtics victory would grab back home-court advantage for Boston, potentially raise further questions about Embiid’s game-worthiness in coming back from a sprained right knee and shift the tougher postgame moments to Rivers’ pressers.

A bounce-back by Philadelphia would either demonstrate Embiid’s improved condition or buy him a little more time in a trek to full health. It would put more urgency into the Celtics’ need to win at least one on the Sixers’ floor. And it would probably tell everyone more about Philly role players Tyrese Maxey, Paul Reed, De’Anthony Melton and Georges Niang, who combined for just 24 points one game after totaling 56.

“Should we just play different the rest of the year now?” Rivers asked media Thursday at the team’s practice facility. “Or should we play the way we played all year, you know what I mean? It’s not rocket science, and it’s not that hard to do.”

There are adjustments to be made. The Sixers’ spacing was too bunched and overloaded to allow for the clean shots and lanes they had in Game 1. And beyond Tucker’s defensive work against Jayson Tatum (seven points, 1-for-7 shooting), most of his teammates could stand to boost their effort, too.

“They pushed us all around. They rode us off of spots,” Rivers said. “We couldn’t get organized because of their pressure.”

Subconsciously at least, however, the Sixers knew by Monday they had accomplished the first goal of every series underdog: Split the first two. And with Embiid riding in as cavalry for Game 2 — not quite ready beyond the bugler — they no longer felt desperate. That was enough.

“A great college coach who I talk to all the time, last night he was like, ‘Man, human nature is a mother,’” Rivers said. “No matter how much you fight it, it just is. Having said that, now it’s even, and both teams believe they can win this series. So let’s get it on.”

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Steve Aschburner has written about the NBA since 1980. You can e-mail him here, find his archive here and follow him on Twitter.

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