MIAMI — On the morning of what could have been their last day at work, Boston’s Marcus Smart and Jaylen Brown leaned into their city’s baseball history.

The Celtics entered Tuesday’s matchup in the Eastern Conference finals down three games to none against the Miami Heat. Since no team in NBA history has successfully climbed out of that kind of deficit, Smart and Brown sought inspiration from another sport. In 2004, the Boston Red Sox pulled off one of the greatest comebacks of all time, rallying from a 3-0 deficit in the American League Championship Series to beat the New York Yankees before going on to win the World Series. Back then, before Game 4, Kevin Millar famously proclaimed, “Don’t let us win today.”

On Tuesday morning before their Game 4, Brown and Smart went for the remix, adding their own spin to Millar’s quote. Brown replaced the “today” with “tonight.” Smart made sure to lock eyes with a reporter as he said, “Don’t let us get one.” The confidence, it would seem, never wavered.

That evening, the Boston Celtics appeared again. It was the same Celtics team that had played throughout the regular season with an identity and a defensive constitution. For the first time in this series, that team showed up, blustery as ever but backing up its big words with a 116-99 win.

“Big win. Big win. Anytime you get the win in the playoffs, it means a lot,” Brown said. “Definitely with our backs against the wall, we didn’t want to go out like that.”

The Celtics held off what would have been an embarrassing sweep, if an expected one, considering how poorly they had played through the previous three games. An hour and a half before the start of Game 4, the doors of Kaseya Center opened and confidence streamed in. As fans, mostly clad in white, walked the concourse, a spontaneous chant of “Let’s go Heat” would break through and catch on. One employee, using her broom as a prop, yelled something to the effect of the Heat sweeping the Celtics. And since fans ate it up, she kept the bit going all the way up until tip-off.

South Floridians came dressed for the occasion – continuing the “white hot” tradition through the playoffs – and ready for a coronation and the franchise’s seventh conference championship. But, for a night, Boston played like Boston. Though the Heat had their moments, the Celtics never allowed a nine-point third-quarter deficit to snowball into a blowout. Instead, they stifled Miami – blocking eight shots and collecting eight steals – and mirrored the kind of team they were in the regular season, when they ranked second in defensive rating.

“Regardless if the ball goes in, you have to defend,” Celtics Coach Joe Mazzulla said. “So we didn’t do that at times throughout the series, and I thought tonight we did that, which, empty possession or not, we still guard at a high level. When we’re at our best, that’s what we do, and that’s what we have to do.”

Even more, the starting five showed offensive balance, as the entire group scored in double digits. Boston didn’t allow a slow start from beyond the arc to deter its thirst for 3s and connected on 18 shots from long distance. And Celtics star Jayson Tatum finally scored a bucket in the fourth quarter. In fact, he went 5 for 7 from the floor for 11 of his game-high 33 points.

So, where have these Celtics been all series? Or a better question: Can this same Boston team do it again for three more games?

“Now we’ve just got to go win another one. That’s all that matters. We take it one game at a time,” Smart said. “We understand the odds are stacked against us, but we’re a team that believes in us no matter what, and we’ve just got to keep going, and all that matters is the next game.”

For all the boldness that oozed out of the Celtics, Miami’s Jimmy Butler still looked and sounded as assured as he’s been throughout the playoffs. In the final minute of the game, with the little-used role players getting some run, the TNT broadcast showed Butler and teammate Gabe Vincent smiling at something while on the bench. They didn’t seem to be worried at all about a possible Boston resurgence. Later, as he addressed the media, Butler explained his nature. He stays even-keeled. Whether it’s getting the sweep at home, or preparing for the series to shift back to Boston for Game 5, he’s going to be himself.

“Stay consistent. Do the same thing that I do, that we do, after every game. We are going to listen to some music. We’re going to drink some beers back there. We are going to go have some wine,” Butler said. “I don’t think that you can just focus on basketball all the time. You have to be able to get away from the game a little bit. Think about it, but at the end of the day, you fall back on your habits, how consistent you’re going to be. Myself and my teammates, we’re going to do the same thing. We’re going to smile. We’re going to be in this thing together like we always are, and we are going to go get one on the road.”

The day started with Smart and Brown sounding like baseball players, and ended with Butler smiling in the face of defeat, then downing an adult beverage. Both were displays of confidence: From the team needing to talk itself back up, and the unbothered star knowing his eighth-seeded upstarts won’t cave in so easily. Still, Miami might not want to let Boston win on Thursday.

Just ask the Yankees.