It’s done. The numbers are clear. The Boston Celtics are on the verge of celebrating their 18th championship, possibly very soon. They hold a 3-0 lead in the NBA Finals, a lead that no team in NBA history has ever squandered.

The statistics are undeniable.

Credit to the Celtics, they’re not taking anything for granted.

On what might be the penultimate day of the NBA’s 78th season, the Celtics — who could wrap up the series against the Dallas Mavericks in Game 4 on Friday night — were focused on maintaining their usual routine, despite being just one win away from their first title in 16 years.

“At the end of the day we’re the most vulnerable in this,” said Celtics coach Joe Mazzulla, who, at 35, could become the youngest coach to win a title since Bill Russell did as a player-coach for Boston in 1969. “So, we have to remain with a sense of urgency. We have to have an understanding of our environment. We have to know that we’re just as vulnerable as anybody else in this situation, and how we handle that will determine our fate.”

His message: Stay focused. A team that has gone 79-20 in its first 99 games of the season — on track for the second-best single-season record in Celtics history — would do well to continue their winning formula one more time.

“Either you survive or you don’t,” said Celtics forward Jaylen Brown, echoing something Mazzulla told the team earlier Thursday. “That resonates with me.”

It might seem surprising that the Celtics — the team up 3-0 — are discussing survival and vulnerability. The reality is that it’s the Mavericks who are in a corner no NBA team has ever escaped from.

They’re 0-5 against Boston this season. They’ve been outscored nearly 2-to-1 from 3-point range in this series. They watched a 13-point lead turn into a 21-point deficit on their home court in Game 3. It’s difficult to find any silver lining, though the Mavs insist they still have hope.

“We’re not in the offseason yet,” Mavericks star Luka Doncic said. “They’ve still got to win one more game. Like I said, we’re going to believe until the end.”

There were no concession speeches from Dallas on Thursday, no signs of surrender. But there was an understanding of how steep the challenge is — down 0-3, a deficit no NBA team has ever overcome.

Boston nearly did it last year, rallying from a three-game deficit to force a Game 7 at home against Miami in the Eastern Conference Finals, only to lose. And that followed the Celtics’ loss in the 2022 NBA Finals to Golden State, that series ending in Boston as well. Those were learning experiences. These finals will be one as well for the Mavs.

“When you look at the Celtics, they lose to the Warriors two years ago. They lose to Miami in Game 7 (last season). So, it’s just experience of understanding that you’re not promised to get back, that you’ve got to work,” Mavericks coach Jason Kidd said. “You see the group that is out there today. They know how to play. They’re a really good team.”

By Friday night, they could be a championship team.

The only way for the Celtics to lose this series is if they drop the next four games. Ignore the stat about teams with 3-0 leads in a best-of-seven series being unbeatable — 156 teams have gone up 3-0, 156 teams have eventually won that series. Consider this instead — the last time the Celtics lost four consecutive games in the same season was in May 2021, two coaching changes and a major roster overhaul ago.

“I think from our experiences over the past couple of years, the thing that we’ve really gotten a lot better at is not relaxing, not being complacent. From game to game or series to series, we always want more,” Celtics forward Jayson Tatum said. “Maybe in recent years we took things for granted at some points or were happy to make it to certain rounds, where (now) we’re not satisfied. Even now up 3-0, nobody is celebrating or anything. We still feel like there’s a lot more that we can do. There’s a lot more that we want to do.”

There’s really only one thing left for this Celtics team to do. One more win and Banner 18 — one that will break the tie with the Los Angeles Lakers for the most championships in NBA history — will finally be theirs.

Mazzulla doesn’t care when it happens, just that it happens.

“There’s four rounds left in this fight,” he said. “And however long it takes, whatever it takes, we’ll see how it goes.”