BOSTON — The Philadelphia 76ers have the NBA’s second-best regular-season record (300-173, .634) over the last six seasons, just five games worse than the Milwaukee Bucks’ mark.

The Bucks, of course, have a championship. So do the teams — the Raptors, Warriors and Lakers — with the fifth, eighth and 10th best records, respectively, during that stretch. Four other teams — the Celtics, Cavs, Heat and Suns — have reached the NBA Finals. Another six — the Hawks, Mavs, Nuggets, Rockets, Clippers and Blazers — have reached the conference finals. That’s 14 different franchises that have reached the Eastern or Western Conference finals since the 2017-18 season.

The Sixers still aren’t one of the 14, because they came up short once again, getting absolutely clobbered in the second half of Game 7 of their conference semifinal series against the Celtics on Sunday afternoon.

Having done the clobbering, the Celtics are going to the Eastern Conference finals for the fifth time in the last seven seasons. They had a brutal performance in Game 5 of this series and trailed Game 6 in Philadelphia with less than five minutes left. But Jayson Tatum caught fire just in time and then remained aflame throughout Game 7, leading the Celtics to a a 112-88 victory with 51 points, the most any player has scored in a Game 7 in the playoffs in NBA history.

The Celtics will now meet the Miami Heat in the Eastern Conference finals for the third time in the last four years. That series begins in Boston on Wednesday (8:30 p.m. ET, TNT).

Here are some notes, quotes, numbers and film from a game that escalated quickly … as well as the aftermath for a team that just hasn’t been able to get over the hump.

1. Third-quarter avalanche

The Sixers led Game 7 by nine points early in the second quarter, and were still up by two late in the period. But the Celtics scored the final five points of the half to take a three-point lead into the break.

Philly tied the game with a Tobias Harris 3-pointer on the first possession of the third quarter. And then things fell apart. On one end of the floor, the Celtics scored 24 points on 13 possessions, shooting 6-for-7 from 3-point range. On the other end of the floor, the Sixers scored just once on a stretch of seventeen possessions.

Thirty-five seconds into the third quarter, the game was tied. And with 35 seconds left in the quarter, the Celtics were up 28. It was an onslaught, and the effects of it could be seen in the body language of the Sixers, who looked defeated well before the series was officially over. The nadir may have been a backcourt violation when Joel Embiid passed the ball to James Harden, who had yet to cross the mid-court line.

“I actually thought it started in the second,” Sixers coach Doc Rivers said of his team’s collapse. “We were playing so well. We trusted, the ball was moving. Then we had three or four turnovers in a row… After that, we never played right again.”

In total, the Celtics scored 13 times and had zero turnovers in the third quarter. The Sixers scored four times (shooting 3-for-21) and had seven turnovers.

2. All Tatum, all the time

Seventeen of the Celtics’ 33 third-quarter points came from Tatum, who already had 25 at halftime. It was one of those games where he was scoring from everywhere. Drives, post-ups, step-back jumpers. He had been in and out of this series, and shot just 42% through the first six games.

But he came up huge when the Celtics’ season was on the line, both at the end of Game 6 and again on Sunday, when he shot 11-for-18 inside the arc, 6-for-10 from 3-point range, and 11-for-14 from the line.

“I was too locked in, too tight,” Tatum said of his struggles in the first 43 minutes of Game 6. “Today I was more myself … That’s when I play my best, when I’m having fun.”

It was the eighth 50-point game of Tatum’s career. Three of those have come in the Play-In Tournament (1) or the playoffs (2). Three other active players – Damian Lillard, Donovan Mitchell and Jamal Murray – have multiple 50-point playoff games, though each of those guys are 1-1 in those games, while Tatum is 2-0.

JAYSON TATUM HAS 51 POINTS 😱

THE MOST EVER IN A GAME 7. HISTORY.

📺: Live on ABC pic.twitter.com/7CHmfr0GiE

— NBA (@NBA) May 14, 2023

“He was fantastic tonight,” Embiid said. “He chose a great night to have that type of game and make shots.

Asked if he’d seen anything like what Tatum did in a playoff game, Rivers had an answer.

“I’ve seen one,” he said. “It was in this building, unfortunately, and it was LeBron.”

That would be LeBron James’ performance — 45 points, 15 rebounds, five assists — in Game 6 of the 2012 Eastern Conference finals, when his Heat were facing elimination against Rivers’ Celtics. Miami would go on to win the series and, eventually, James’ first championship.

James was 27 years old at the time. Tatum is just 25, also seeking his first title.

3. Attacking the MVP

A big reason why Embiid won the Kia MVP award this season is that he’s a two-way star, the league’s leading scorer and a great interior defender. But if there’s a weakness to his game it’s his difficulty defending in space … which is precisely what the Celtics made him do a lot in Game 7.

On their sixth possession of the game, Robert Williams III (being defended by Embiid) set a screen for Tatum, who blew right past the Sixers’ big man for a dunk…

On the next possession, Embiid was guarding Al Horford, and Tatum called for another screen. Instead of obliging, Horford caught Embiid sleeping, cutting back door. He drew help from Tobias Harris and dropped the ball off to Williams for another dunk…

The Tatum-vs.-Embiid pick-and-roll really picked up in that deciding third quarter. Tatum wasn’t afraid to attack, drawing a foul and getting to the line…

The Sixers tried switching the action, only for Embiid to get burned. They tried double-teaming Tatum, only for the Celtics to find an open shot elsewhere. They played zone, and that didn’t work.

“Once we fixed our spacing and our intentionality on offense,” Celtics coach Joe Mazzulla said, “that’s when we broke through.”

According to Second Spectrum tracking, the Celtic that Embiid was defending had set 33 ball-screens for Tatum through the first six games, with a maximum of 11 in any single game (Game 3). And Boston scored a paltry 0.87 points per chance with that action.

In Game 7, Embiid’s man set 18 ball-screens for Tatum, and the Celtics scored 1.47 points per chance on those plays.

“We didn’t handle it very well,” Rivers said. “It’s the same coverages that we’ve been in all year and all series. And we’ve been very effective at it.

“I thought there was fatigue on our end, and I thought that hurt us. But they were effective in everything they did.”

Whether it was fatigue or the lingering effects of the knee injury he suffered in Game 3 of the first round, Embiid was not moving well defensively.

“No excuses,” Embiid said. “I thought I was OK. I thought I was limited, for the most part, not just tonight but since I came back.”

This, of course, was not the first postseason in which Embiid had injury issues.

“The kid deserves a break,” Rivers said. “He really does. He deserves one shot to just be 100 percent throughout. I don’t know if we would have won this series. But I would just love to have one time where we don’t have issues. I haven’t had that opportunity and Joel hasn’t had that opportunity. And that sucks for everybody.”

4. An uneven series

This was a seven-game series in which the overall point differential was 62. The Celtics’ four wins came by an average of 19.8 points, while the Sixers’ three wins came by an average of 5.8.

Save for Game 6, the Celtics scored pretty consistently throughout the series. The big difference was on the other end of the floor, where the Sixers scored 124.1 points per 100 possessions in their three wins and just 95.8 per 100 in their four losses.

In the regular season, Philly scored less than a point per possession in four of its 82 games. In this series, the Sixers scored less than a point per possession in three of seven.

5. Big decisions to be made

After coming up short once again, the Sixers face an offseason filled with big questions. They had a terrific summer in 2022, re-signing James Harden at a discount and adding quality depth. And they ended up in same place as they were a year ago, getting bounced in the conference semis. It’s now been 10 years since “The Process” began with Jrue Holiday being traded to the New Orleans Pelicans. (A year prior to that, the Sixers lost to the Celtics in Game 7 of the conference semis.)

Harden has a player option in his contract that he can decline to become a free agent. A year ago, he scored zero points in the second half as the Sixers were eliminated in Game 6 vs. Miami. On Sunday, he had another quiet elimination game, scoring just nine points on 3-for-11 shooting and turning the ball over five times.

But Harden’s pick-and-roll playmaking is a big reason why Embiid is the MVP. He’s made the big man a more efficient scorer by getting him more catches closer to the basket.

“We got an unfinished job,” Embiid said of his partnership with Harden. “We haven’t won anything, and I think we got the chance to win. Going to seven games and having a chance to close it out at home, which we didn’t do, I still believe we got the chance to win. We got what it takes to win.”

“I just want to have a chance to compete,” Harden said with some equivocality.

Rivers will surely face scrutiny. Two coaches who faced each other in the Finals just two years ago – Mike Budenholzer and Monty Williams – lost their jobs in the last 10 days. Few coaches go out on their own terms.

“No one’s safe in our business,” Rivers said. “And I get that.”

But he seems to have Embiid’s endorsement.

“I thought he’s done a fantastic job,” Embiid said. “I think we’ve gotten better over the years. I thought he’s done a great job. I don’t make the decisions and I think he should be fine.

“You look at the way he handed the whole situation that we had a year or two ago. He kept this team afloat and he’s been a leader for all of us, a great motivator.”

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John Schuhmann is a senior stats analyst for NBA.com. You can e-mail him here, find his archive here and follow him on Twitter.

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