MIAMI — No NBA team ever has climbed all the way out of a 3-0 hole to prevail in a best-of-seven playoff series. One-hundred-forty-nine have found themselves in position to try, and all 149 have failed.

Then again, no NBA postseason ever has featured two sweeps in the conference finals. As a result of Miami’s 128-102 drubbing of the Boston Celtics at Kaseya Center Sunday in Game 3 of the Eastern Conference Finals, the Heat and the Denver Nuggets both are up 3-0, on the brink of bilateral broomings.

So there still is hope for a little we-never-have-seen-that-before basketball history to be made in the next couple days. When the insiders and pundits start debating which of the beleaguered — the Los Angeles Lakers or the Celtics — is more likely not to get swept, you know their respective opponents are firmly in control, playing at impressive levels and not inclined to suffer letdowns that would qualify in any way as serious.

For the record, only three of the aforementioned 149 teams that trailed 3-0 managed to even tie their series, forcing a Game 7. The Knicks rallied enough against the Rochester Royals in the 1951 Finals to do it, Denver in 1994 recovered to push Utah to the brink in their West semifinals series and, in 2003, Portland fell behind 3-0 but forced Dallas to the limit before succumbing.

The closest the league ever has come to having two sweeps in the conference finals — covering all postseasons with the 16-team format — was in 2015. Cleveland and Golden State raced to 3-0 marks against Atlanta and Houston, respectively. But while the Cavaliers swept the Hawks, the Warriors needed an extra game to polish off the Rockets.

That might not be much, but it’s something for the Lakers and the Celtics to show up for in their Game 4s.

Meanwhile, here are five takeaways from the Heat’s Game 3 victory, a performance so thoroughly dominant over Boston that it might have counted as two.

1. The Celtics’ heart needs a paddling

While the rest of us were wondering just where Boston’s collective heart was Sunday, its players and coaches weren’t puzzled at all. That’s because Miami reached in, grabbed hold and pulled it right out of their chests in the third quarter last night.

Granted the winners won’t actually show the no-longer beating organ to the Celtics until Tuesday or whenever exactly Miami wraps this surprisingly lopsided series. But the end is near, as evidenced by all that the Celtics haven’t bothered or been able to do so far.

They opened at home, heavily favored over the East’s No. 8 seed, and lost both. Then they faced essentially a “must win” situation in Game 3 — the whole NBA world knows that 3-0 is a historically impossible series deficit — and turned in one of the worst showings in the storied Boston franchise’s long playoff history.

Even trying to turn what normally would be a negative, playing on the road, into a positive — Boston came in 12-6 in away games over the past two springs — fell sadly short.

Player after player said afterward that the Game 3 egg they laid was on them. But that didn’t stop coach Joe Mazzulla from sounding like a guy issuing a steely decline when asked if he wanted a blindfold for what comes next.

“I just didn’t have them ready to play,” Mazzulla said several times. “Right now, they have a mentality and we don’t.”

One step away from the Finals, there scarcely could be a worse admission at a worse time, but that’s where it stands.

Frankly, it shouldn’t be on Mazzulla to do all the heavy lifting, not with proven veterans and talented stars up and down his roster. But several established NBA coaches have been fired for less dramatic fizzles than Boston’s. Anything less than a complete comeback — that’s right, becoming that very special first of 150 teams to actually climb out of their postseason graves — would start the Celtics’ 2023-24 season with an insurmountable elephant in the room.

2. Miami’s killer non-Bs

That was Miami coach Erik Spoelstra’s term for his team’s “others,” as in fellows not named Butler or Bam. Spoelstra long ago got tired of being asked about the likes of Gabe Vincent, Duncan Robinson, Caleb Martin and Max Strus all going undrafted before they turned various toeholds in the league into vital roster spots for the Heat.

To label them forever for the scrambles that got them here seemed undignified. Yeah, “non-Bs” is better.

They were better than Boston Sunday. Vincent scored a career-high 29 points, hitting 11 of 14 shots and six of his nine 3-pointers. All by himself, he outscored Celtics stars Jayson Tatum (14 points) and Jaylen Brown (12). Yet Vincent had plenty of help, with Robinson scoring 22 and Martin 18.

Those three combined to take 36 shots for Miami, double the number put up by Jimmy Butler and Bam Adebayo. And it was good.

“Jimmy and Bam are both fueling that,” the Heat coach said. “They are just infusing those guys with confidence.

“Y’know, we talk about it all the time. You want to breathe life into other guys, and ultimately enjoy someone else’s success, but that takes great emotional stability. … You’re seeing some of the role players really grow and be able to expand their games. That only happens if your star players really want that.”

With Tyler Herro (hand surgery) and Victor Oladipo (knee surgery) both out, the emergence of additional threats — more of a revival in Robinson’s case — makes Miami’s offense much more ready for basketball in June.

3. Boston’s non-killer Js

Anyone who has second-guessed the folks who voted Philadelphia’s Joel Embiid as the NBA’s 2023 Kia Most Valuable Player — based on the Sixers’ flop from a 3-2 edge in the East semifinals and Embiid’s rather ordinary performance — might want to send some of that vitriol Tatum’s and Brown’s way.

The former finished fourth in that MVP balloting and was named All-NBA first team. The latter wasn’t far behind, snagging a second team All-NBA spot. But throughout the league and even in Boston, folks are wondering if the two are overrated in general or simply flopping at the most embarrassing time.

Brown actually used that word, though in general terms, for what he and his teammates did — more precisely, didn’t do — in Game 3. “I don’t even know where to start,” he said. “An obvious letdown. I feel like we let our fan base, organization down, we let ourselves down, and it was collective. We could point fingers, but in reality, it was just embarrassing.”

After three games of this series, the two Celtics have shot a combined 7-for-40 on 3-pointers, including 1-for-14 Sunday. They have taken 116 shots to score their 128 points, they’re shooting 41.4% overall and they have a total of 21 assists to 23 turnovers.

Sure, Tatum and Brown are the first two orders of business on Miami’s defensive to-do list. But it’s more than that. Brown has slipped and slid at times as if on skaters. Tatum, normally so smooth, has seemed more than once in need of an oil can when going up for shots.

“Tonight was tough,” Tatum said. “I think from the beginning of the game, we were turning the ball over. We didn’t shoot the ball well. They shot the ball extremely well. Just kind of felt like we never recovered, honestly.”

Malcolm Brogdon, the NBA’s Sixth Man of the Year and yet another Boston “B,” sputtered along with a scoreless 0-for-6. Still, the burden falls most of all on the two young stars, a status that might get dinged over a cranky Celtics summer.

Tatum shared Sunday that he deleted the Twitter app from his phone at the start of the playoffs. Might want to keep it that way right up to training camp.

4. Going 3-point crazy

That has dual meaning to this point. Miami has been out-of-character good from the arc so far, sinking 19 of 35 in Game 3 and 44 of 92 overall. That’s a staggering 47.8% for a team that hit only 34.4% during the regular season, when it ranked 27th in its accuracy. The Heat also ranked 17th in 3-pointers made per game (12.0), compared to 14.7 now.

At the other end of this spectrum, Boston leaned on 3-point prowess for much of its season success. Mazzulla, despite his taciturn demeanor, focuses more on offense than on defense and wants to see the Celtics let it fly. That worked from October into April, when they took and made the second-most threes in the league, making them at a 37.7% clip.

In these three games? They have made 31 3-pointers, 13 fewer than the Heat, and shot them at 29.2% pace. Which is why it was so confounding for them to keep jacking them up Sunday, 11 for 42 (26.2%) by the end. Yes, the score got out of hand, but they seemed unwilling to force things along two points at a time.

5. Yes, they have to play Game 4

It will seem like a formality if Boston doesn’t show up with more energy and more effort, especially on the defensive end. Its lethargy — particularly after giving up a 28-7 Miami run through the heart of the third quarter — had the Heat’s attackers looking like San Antonio’s “beautiful basketball” crew of 2014 for how they moved the ball and shared the Game 3 shot chart.

Can the Celtics force Miami to go back to Boston with them for a Game 5? Not from the looks of it at this point. And even if they mustered the will to try, the real question is, will the Heat allow it? Miami has a chance not just to return to the Finals for the first time since the locked-down Orlando bubble in 2020. It could earn itself a full week off before Game 1 of the championship round starts on June 1.

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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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