The Celtics blew a 22-point lead and are still having the fifth-best regular season of all time

ALL STEPHEN CURRY could do was shrug.

It was Sunday inside the TD Garden visiting locker room, and the NBA-leading Boston Celtics had just handed the Golden State Warriors their worst defeat ever with the two-time MVP in the lineup. The 140-88 drubbing featured 10 3-pointers in the first quarter and a 61-17 run over an 18-minute span that sealed the Warriors’ fate by halftime.

“That’s what we used to do to teams,” Curry, the maestro of similar scoring runs during Golden State’s march to four championships in eight seasons, said from his locker after the game.

“It’s kind of demoralizing.”

Boston’s victory on Sunday gave it three wins of at least 50 points this season, already the most in NBA history with over a month remaining in the regular season. Meanwhile, the Celtics’ point differential of plus-243 during their 11-game win streak also set a league record.

Boston leads the league in offensive efficiency, is second in the league in defense and is putting up historic point differentials.

But Boston enters Thursday’s road meeting with the Denver Nuggets — a showdown of the top title favorites — having played arguably its worst quarter of the season, particularly highlighted by the late-game struggles of superstar forward Jayson Tatum.

On Wednesday, just two days after that 52-point win over Curry’s Warriors, the Celtics let a 22-point lead slip away in the final nine minutes against the short-handed Cleveland Cavaliers, a collapse capped by Tatum’s failed game-winning contested fadeaway in the final second.

“Just a weird way to end the game,” Tatum said of the 105-104 loss. “But they always say the game isn’t won or lost on the last play.”

Boston’s status as a juggernaut is undeniable. Since 2016-17, Jaylen Brown‘s rookie season, the Celtics have the NBA’s best regular-season winning percentage, and only the Warriors have won more playoff games.

But until this team wins that elusive 18th banner, this group of Celtics players will be judged by how they finish things off — whether it’s protecting a fourth-quarter lead in March or successfully closing out a playoff series in May and June.

“Your habits are everything,” Brown said of the Celtics’ task ahead as they prepare for the postseason. “Your mentality is everything. And every game, you can’t waste no possessions, you can’t waste no time out there on the floor.”

THE NBA HASN’T seen many regular-season runs like the 2023-24 Celtics.

Despite Tuesday’s loss, the Celtics’ point-per-game differential this season (11.2) is the fifth largest in league history behind a quartet of iconic championship teams: the 1971-72 Los Angeles Lakers (12.3), the 1970-71 Milwaukee Bucks (12.3), the 1995-96 Chicago Bulls (12.2) and the 2016-17 Warriors (11.6).

The Celtics, on pace for 66 wins, would become the 18th team in league history to reach that mark. Of the 17 previous 66-win teams, 12 went on to win the championship that season. In short: It’s been a dominant showing through the first three quarters of the regular season.

For Celtics big man Kristaps Porzingis, who joined a lineup that also added former champion guard Jrue Holiday this summer, the group’s ceiling was visible right away.

“We have to give a lot of credit to our front office for putting this type of team together,” Porzingis said on Feb. 24 after a win over the New York Knicks. “When the opportunity [to join Boston] was presented, for me at least, I said this is going to work, 100 percent.”

And in today’s NBA, the most versatile and malleable lineups are often the most successful. No team embodies that better than these Celtics.

Boston’s top eight rotation players — Tatum, Brown, Holiday, White, Porzingis, Al Horford, Sam Hauser and Payton Pritchard — are each attempting at least five 3-pointers per 36 minutes, and all but Brown (35.4%) are shooting 37% or better from deep.

Not surprisingly, the Celtics are leading the league in 3-point makes (16.3) and attempts (42.3) per game, while sitting fourth in the league by making 38.6% of their looks from deep. And having so many shooting threats across the board means teams will pay the price for trying to focus their attention on Boston’s two main offensive engines, Tatum and Brown.

Or, they’ll have to try something like Golden State did Sunday, essentially deciding it was worth daring Brown to shoot and living with the results — only for him to immediately bury five 3s to put the game out of reach.

“If you want to dare me to shoot, we can do that,” Brown said after Sunday’s win.

The group’s defensive versatility has also given opposing teams headaches.

Consider Tuesday’s game in Cleveland. Boston stuck Holiday on Cavaliers forward Isaac Okoro, a defensive wing, for large stretches, allowing Holiday to roam and play help defense. That was because Boston could put either Brown or White on Darius Garland, Cleveland’s elite perimeter ball handler.

With Holiday and White, two of the league’s best individual on-ball defenders, in the starting backcourt, Boston can attack teams in ways few others can defensively. Overall, the Celtics have blitzed a total of just 47 ball screens this season, per Second Spectrum’s tracking data (1.1% of time, the second-lowest total in the league). When the starting five is out there, they’ve blitzed only five ball screens all season (0.66%).

“The amount of confidence that they play with, and how every single guy on their team has bought into their role,” Cavaliers coach JB Bickerstaff said before Tuesday’s game of what has impressed him about the Celtics.

“They know who they are. They know how talented they are, but they allow each other to be successful in their own spaces.”

THE END-OF-GAME SEQUENCE on Wednesday showed similarities to another one-possession game that Boston failed to secure six weeks ago. At home against the Nuggets on Jan. 19, Boston missed eight of its final nine shots, but — like against Cleveland — still had a chance to tie or win the game with 4.9 seconds remaining.

Like in Cleveland, the ball was in Tatum’s hands as Boston settled for an uneven possession — a fallaway jumper that he later admitted was rushed.

“In the back of my mind, I wasn’t sure if they were going to foul,” Tatum said then. “They had a foul to give. But I had more time than I gave myself, so I should have taken some more time.

“But, can’t go back. Something I can learn from.”

Tatum’s clutch-time stats aren’t pretty. This season, he has shot 15-for-46 (32.6%) in clutch time this season, including 0-for-2 on Tuesday. Among the 25 players who have taken at least 45 clutch-time shots this season, Tatum ranks last in field goal percentage.

And Tatum’s clutch-time woes are not isolated to this season. His clutch field goal percentage over the past three seasons ranks in the bottom 10 among more than 70 players with at least 100 attempts.

The Celtics will still potentially have to get through superstars such as Giannis Antetokounmpo, Joel Embiid and Jimmy Butler to make it back to the Finals. And Boston’s depth could be challenged, particularly at center if Porzingis misses any time.

Yet, the Celtics remain in an enviable position, 7.5 games ahead of the second-place Bucks, with home-court advantage essentially assured as they home in on the playoffs — where, finally, they’ll hope to raise the franchise’s 18th championship banner in June.

That’s why the messaging coming from this group hasn’t wavered through the highs of winning streaks and 50-point blowouts and the lows of late-game collapses such as Tuesday in Cleveland: All that matters, after years of regular-season success followed by postseason heartbreak, is how the Celtics finish.

“Pretty confident in our group the whole year,” White told ESPN after Tuesday’s loss, when asked if the team’s recent win streak changed his opinion about its ceiling.

“We’re just playing good basketball. We just want to continue it and just try to play our best basketball by the end of the year.”

ESPN’s Kendra Andrews and ESPN Stats & Information contributed to this report.