Joel Embiid yearns to finally reach the conference finals and more, while the Celtics’ current core aims to claim an elusive title.

BOSTON – Legacies and narratives will be on the line when the Philadelphia 76ers and Boston Celtics meet Sunday afternoon at TD Garden (3:30 ET, ABC).

As if the basketball implications won’t be significant enough when the teams battle in Game 7 of their Eastern Conference semifinals series, right? The winner advances to the East finals against Miami, the loser heads into summer well shy of its championship goal.

Through six games, both teams have played well on some nights and looked horrible on others. The Celtics and the Sixers each have lost twice on their own court. Boston was stunned when Philadelphia grabbed Game 1 without Kia NBA MVP Joel Embiid back on May 1, and shocked when its team played possibly its worst game of the season Tuesday in Game 5, giving the Sixers’ two cracks at clinching.

They needed them, too, due to their dismal offensive performance Thursday. In the 95-86 loss in which it shot 36% overall and made only eight of 34 3-pointers, Philadelphia dialed up its degree of difficulty, bungled its home-court edge and now is 48 minutes away from being 22 years away (or more) from reaching the conference finals.

The Celtics, meanwhile, won’t be permitted to count the next round as any sort of success. After all, they reached the Finals last June when they all had a year’s less experience and with a first-year head coach who was a) let go for non-basketball reasons, and b) already has the same job with another club.

This is where the legacies and narratives kick in. Can Joe Mazzulla get Boston to the championship round the way Ime Udoka did last spring? What will it say about Celtics management’s decision to promote the 34-year-old, possibly prematurely, or at least bring in a former NBA head coach or two to sit next to him through this 2022-23 run?

When a guy who was on Boston’s bench last year decides a dozen games into these playoffs to start Al Horford and Robert Williams III together – as his big move – it doesn’t instill a lot of confidence from many Celtics fans. Williams’ teammates sounded thrilled and relieved that Mazzulla went that way, and even Derrick White – who flipped into a bench role – felt it was the right decision.

And what of Boston’s star wings, Jayson Tatum and Jaylen Brown, the foundation on which this roster is built? They have All-NBA status and looming mega-max contracts on the way, but at 25 and 26 respectively, have they improved enough to continue spearheading a shot at the franchise’s 18th NBA title (and first since 2008)? Each has gone missing in key stretches, neither more so than Tatum’s 1-for-14 shooting stretch until his flurry of 3s deep into fourth quarter of Game 6.

Then there are the Sixers. They played well enough defensively to win Game 6, but that offense was a mess. James Harden was on his down cycle again. He has had two throwback scoring games in the series (45 points in Game 1, 42 in Game 4), one efficient, “new iteration” of The Beard (Game 5) and three clunkers in which he shot 9-for-44 (20.5%) and averaged 13.7 points.

Mid-range shots that Embiid kept making in Philadelphia’s Game 5 victories to fend off a Celtics comeback were bouncing off in Game 6. Afterward, he talked about not touching the ball in the game’s final four minutes and he nearly nailed it – he missed the last of his 19 attempts down 84-83 with 3:56 to go. Boston outscored his team 11-3 from there.

His 26 points and 10 rebounds were shy of his MVP averages, and much of the onus for his late absence from the attack was on him. Embiid should be getting to the low post and demanding the ball more. He has 11 offensive rebounds in the series, one fewer than Tatum, which limits his touches too. The biggest player on the floor has not played with full force so far.

As for Mazzulla’s counterpart, Sixers coach Doc Rivers, there is a narrative in play if not a legacy at stake. Rivers ranks ninth all-time in NBA victories, one of 10 men who have won more than 1,000 games – and the other nine all are in the Hall of Fame already. But his teams have lost nine times in Game 7, four more than any other coach.

And when on the brink of reaching a conference finals, those teams have dropped nine games in a row.

Asked before Game 6 about Mazzulla’s limited experience, Rivers said: “When you get a young coach, everything that doesn’t happen, it’s his fault. Just like when you get an old coach and everything that doesn’t happen, it’s his fault. That’s just the way it works.

“They look very prepared to me. We’re very prepared. Now it’s time to play basketball.”

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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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