BOSTON -- Joel Embiid had a phone call to make. The Sixers were shipping up to Boston, headed for a showdown with the second-place Celtics, but first the big man needed to clear his mind.

The night before, former NBA greats Shaquille O’Neal and Charles Barkley had made headlines with their blistering critiques of Embiid’s performance during TNT’s broadcast of the Sixers win over the Nuggets. He wasn’t living up to his potential, they said. He was playing as if he was satisfied with being good, instead of yearning to be great. It was the sort of criticism that can dampen a soul: not doubt, or diminishment, but disappointment.

Then a funny thing happened. Embiid listened to their words and found himself agreeing. So instead of cursing or brooding, he picked up the phone. He dialed O’Neal’s number. He assured the Hall of Famer that he was not mad. And then he asked for advice.

“I just wanted to talk to him,” Embiid said. “I’ve been kind of frustrated. ... He was just telling me, ‘Be aggressive. You’re the guy. So just go out there and dominate.’ ”

Twenty-four hours later, that’s exactly what he did. In a 115-109 win over the Celtics on a frigid New England night, the player Embiid’s critics have been clamoring to see returned with a vengeance.

For four quarters, he battered Boston’s unimposing rotation of bigs, marking the paint as his territory with the focused aggression that had too often been absent from his game. Eight of the 12 buckets that he made came at the rim. Sixteen of his game-high 38 points came in the fourth quarter, including a catch-and-shoot three-pointer from the top of the arc that gave the Sixers a 100-92 lead and put the Celtics on the ropes with 4:05 left.

“I haven’t been the closer that these guys have needed me to be the whole season,” Embiid said. “I just had an opportunity and they kept feeding me.”

From the opening tip, Embiid’s focus was evident to all who strayed near it.

“His energy, his interactions at timeouts and dead balls -- he was the man today,” said Tobias Harris, who chipped in 23 points while helping the Sixers improve to 19-7.

There was a moment late in the first half that epitomized the performance. One moment, Embiid was out in front in transition, his long, loping strides carrying him into the paint as Enes Kanter backpedaled between him and the basket. The next, he had Kanter buried, driving his shoulder into the Celtics big man to knock him backwards under the rim, then whirling around to seal him off on his rear. Harris recognized it, got him the ball, and then watched as Embiid tossed an easy baby hook into the bucket to pull the Sixers to within four.

“I just had to be aggressive,” Embiid said. “That’s the right attitude. That’s the attitude I have to have every single night.”

For much of the season, Embiid’s most ardent defenders have cursed the increasing clamor surrounding the Process poster boy’s production. They smirked at the commiseration they sensed from the less enlightened sections of the fan base. What we have here, they said, is a couple of attention-starved men tossing chum to a city that had always been too old school to recognize new age greatness. They pointed to his stat line: 22 points, 12.4 rebounds, 1.4 blocks per game. They pointed to the on/off splits that yet again portrayed him as one of the most impactful defensive players in the league. They pointed to all of the unfriendly variables in play around him: the presence of a point guard who also makes his living in the paint, the lack of three-point shooting throughout the starting five, the poor spacing, the frequent double teams. Embiid, they said, was the least of the Sixers problems.

And while there may be plenty of kernels truth in such claims, they also completely missed the point. The question isn’t whether Joel Embiid is a good basketball player. It isn’t whether he is the best defensive center in the league. No, the question that could very well determine the Sixers’ championship fate is whether Embiid can enter that rarified realm of truly great scorers whose presence on the offensive end of the court is the sort of factor that opponents simply cannot combat.

That’s exactly the sort of player that Embiid was on Thursday night. By the end of the night, the Sixers had outscored the Celtics by 21 points when he was on the court, and had been outscored by 15 when he was off of it.

“For me, (it was) one of his better games since he’s been a Philadelphia 76er,” coach Brett Brown said. “He was dominant, and he was a leader.”

Here’s the bottom line: on the nights that Joel Embiid plays up to his potential, all of the other concerns about this Sixers roster become a lot less relevant. The shooting, the spacing, the odd-fitting parts: Embiid has the physical capabilities to mute them all. If he ever reaches his ceiling, the Sixers are a championship-caliber team regardless of who they put around him.

Those are the expectations, and anybody who sets them lower is guilty of underestimating the big man. The criticisms of Embiid do not reflect a lack of appreciation on the part of the beholder. Exactly the opposite. The criticism stems from a belief that Embiid has it within him to become one of the most dominant players in the history of the game.

On Thursday night, it did not matter what defensive look the Celtics threw at him. Early in the fourth quarter, he had a double team to his front and simply elevated above it and dropped a hook shot over the outstretched hands of the defenders. His final line: 38 points, 13 rebounds, six assists, two turnovers.

Instead of proving his critics wrong, Embiid proved them right.

“For them to say that I have the potential to be one of the best players in the world and I haven’t shown that and I should be already showing it, that says a lot,” Embiid said. “They’ve been there, they’ve done it, they’re Hall of Famers. It just shows me I have to play harder and dominate like I can.”

Later that night, he did exactly that. And after he did, there was no need to question what was wrong with the Sixers. There was no reason to wonder about the spacing, and the shooters, and the odd-fitting parts. You did not need to pore through the rotation and wonder if the Sixers really had the necessary components for a championship team. On Thursday night, against one of their chief rivals for the Eastern Conference crown, all that mattered was that they had Embiid.