Will Doc Rivers and the Sixers finally overcome their string of second-round disappointments?

We’re about to find out if the 76ers are more successful than their recent predecessors.

A lot has been made about the different feel this season. Fans celebrated the Sixers, at 54-28, finishing with their best regular-season record in 22 seasons. The team can boast a league MVP and first-team All-NBA selection in Joel Embiid. And Embiid (33.1 points per game) and James Harden (10.7 assists) became the first pair of teammates to sweep the league scoring and assists titles in 41 seasons.

But none of that will matter if the Sixers don’t close out their Eastern Conference semifinal series against the Boston Celtics. Philly has a 3-2 advantage in the best-of-seven series. It can clinch the series at 7:30 p.m. Thursday in Game 6 at the Well Fargo Center. If the Celtics win, the teams will have a winner-take-all Game 7 on Sunday in Boston.

» READ MORE: Sixers’ Joel Embiid lands spot on All-NBA first team, adding to this year’s list of career milestones

If the Sixers lose the series, this season will have a similarly disappointing ending to five of their last six postseason appearances. Like this season, there each year featured a lot of hype around the team as they entered the postseason. Yet they still concluded with conference semifinal exits.

The Celtics disposed of the Sixers in five games in 2018. The Toronto Raptors eliminated them on Kawhi Leonard’s four-bounce buzzer-beater in Game 7 in 2019.

The Celtics swept Sixers in the first round in the 2020 NBA bubble, leading to coach Brett Brown’s firing. The Sixers had the conference’s best record in 2021, their first season under Doc Rivers. However, the Atlanta Hawks ousted them in seven games in the conference semifinals. And last season, the Miami Heat defeated the Sixers in six games.

But exits in the conference semifinal have been the Sixers’ reality for longer than that. The Sixers are looking to win a second-round series for just the second time in the franchise’s last 13 appearances, dating back to 1986. They beat the Raptors in seven games in 2001 en route to finishing as NBA Finals runners-up.

So there has to be some pressure to close out the series Thursday night and make sure the Celtics don’t gain any momentum with a Game 7 back at TD Garden.

Boston excelled in a similar situation last season. They trailed the Milwaukee Bucks, 3-2, in the conference semifinals. However, they won Game 6 in Milwaukee and Game 7 in Boston to advance to the conference finals.

“We openly talk about it as a group,” Rivers said Wednesday, referring to the Celtics’ success last season. “You know, what do they have to lean on to be confident about? Well, they’ve done this. So they’re going to come in [Game 6] with confidence. We have to be ready for that.

“Still, you gotta get to four [wins] no matter what. No matter how it’s done, you gotta get to four. And [leading 3-2] you hadn’t done anything. We talked about that a lot today.”

» READ MORE: Sixers vs. Celtics Game 5 takeaways: Joel Embiid’s maturity, Tyrese Maxey’s breakout, Tobias Harris’ rebounding

Rivers has remained adamant throughout the postseason that advancing beyond the conference semifinals is not the Sixers’ focus. Their goal, he said, is to win an NBA title.

“It’s not even a concern for us,” he said. “We’re not worried about that. That happens if you win a title. But that’s too shallow of a goal. … I guarantee you, not one guy is talking about that. Like I told you before, half the team hadn’t been here.

“I think when this started, I was playing.”

And he’s right. The former point guard had a 13-year NBA career that ended in 1996.

But this could also be a defining moment for Rivers. He’s been unable to advance to the conference finals in not only his first two seasons in Philly, but the previous seven coaching the Los Angeles Clippers. In 2008, however, he led the Celtics to an NBA championship over the Los Angeles Lakers. His Celtics later lost to the Lakers in the 2010 Finals, and they reached the conference finals two seasons later.

After leaving Boston, Rivers led the Clippers to six postseason appearances in his seven seasons in Los Angeles. They reached and lost in the second round three times. The last two times — 2015 and 2020 — they were a game away and failed to advance, blowing a 3-1 lead both times.

So this could be a monkey-off-their-backs moment for Rivers and the Sixers. But the Celtics are hoping to add to the Sixers’ second-round struggles. And they expect to make things uncomfortable, beginning Thursday night.

“It’s a true dogfight, scratching and clawing, biting, blood, everything,” Boston point guard Marcus Smart said of coming back from 3-2.. “And if you’re not willing to pretty much get dirty, if you’re not willing to bleed, if you’re not willing to break something, willing to tear something, going hard, then you shouldn’t be on that court because that’s what it is.”

So we’ll find out as early as Thursday night if the Sixers will end their misfortune in the conference semifinals.