BOSTON — When the Celtics make a ton of 3-pointers, forget it. They’re probably not going to lose.

That was surely something the Mavericks understood before Game 1 of the NBA Finals — and if they, or anyone else, somehow were unaware of that fact, it was on full display in the opener.

The Celtics made 16 3s, outscoring the Mavs by 27 points from long range, in their 107-89 victory Thursday night. Both teams have an off day Friday and are scheduled to resume practice Saturday. Game 2 is Sunday night in Boston.

“We’ve got to be better,” Mavericks coach Jason Kidd said. “Nerves or not being in this situation, we can’t use that as an excuse. It’s just basketball, and we’ve got to be better at the game of basketball on Sunday.”

And it’ll start with doing a better job on 3s — either making more, giving up fewer, or both. Consider these trends for the Celtics this season:

When making 16 or more 3s, the Celtics are 51-6. When making 15 or under, the Celtics are 26-14. That’s still a very good mark, but at least opponents have a realistic chance of winning when that happens.

When the Celtics make more 3s than their opponent, they’re 61-5. When they don’t, they’re 16-15, basically a coin-flip to see who wins.

When the Celtics make at least four more 3s than their opponent, they’re 49-3.

When factoring in both the regular season and the playoffs, not only have the Celtics made more 3s than anyone else (1,572 so far this season, 24 away from matching the league’s total-season mark the Celtics set last year), but the Celtics also have a better percentage this season than any other club. They’re at .3852 for the season now, a whisker ahead of Oklahoma City’s .3851.

“I think they are the best 3-point shooting team in the NBA, so sometimes (it’s) really hard to take those away,” Mavericks guard Luka Doncic said. “Especially when they have five guys out and they can all shoot. Obviously, we’ve got to make more.”

And it was a team effort for the Celtics in Game 1. That has to be what makes it doubly scary for the Mavs — because just about everyone in the Celtics’ rotation was part of the prowess from deep.

Jayson Tatum and Derrick White each made three 3s, while five other Celtics each made two. It was only the seventh time in NBA playoff history that seven teammates made at least two 3s in a game; it was the second such instance for Boston in this year’s playoffs, and the first time it ever happened in an NBA Finals.

“They are going to make some 3s at times, but we want to make them tough,” Mavericks guard Kyrie Irving said. “When they are at home, they shoot incredibly well.”

The Celtics led by 29 in the first half, then the Mavs got the margin down to eight in the third quarter. It looked manageable — that is, until the Celtics started making 3s again. Tatum hit a 3, pushing the lead to 16. Al Horford hit another, and the lead was 19. Jaylen Brown hit another; lead up to 22.

Crisis averted. Collapse warning lifted. The game wasn’t in doubt again.