The Celtics cannot repeat Game 2′s subpar shooting in Game 3

The NBA, as the last coach to lead the Celtics to an NBA championship liked to say and say often, is a make-or-miss league.

It can sound trite or simplistic, that old Doc Rivers line. It can sound suspiciously like an excuse. It also happens to be true.

Sometimes your five are missing and missing, and their five are making and making, and there’s not a thing Red Auerbach in his prime or any other coach worth his clipboard can do to keep the gap from widening on the scoreboard.

It happens, those rare and lousy nights at TD Garden when the rim is kind only to the visitors.

This much is also true: the Celtics had better hope that the explanation for their 118-94 loss to Donavan Mitchell and the Cavaliers in Game 2 of their Eastern Conference semifinal matchup is no more complicated than this.

The Cavaliers smoked the Celtics in Game 2, turning a 54-54 halftime tie into a rout in front of a TD Garden crowd that was strangely muted by its usual standards even when the game still carried some suspense.

The Cavaliers evened the series (with Games 3 and 4 in Cleveland on Saturday and Monday) by outscoring the Celtics, 64-40, in the second half, and building their lead by as much as 29 points.

Mitchell, who scored 33 points in a losing cause in Game 1, was the best and savviest player on the floor. In the first half, he went out of his way to involve supremely-talented but often laconic teammate Evan Mobley.

Mitchell took just six shots in the first half, but dished out five assists, while Mobley (15 points in 19 minutes in the first half, 21 overall) asserted himself on both ends of the floor.

In the second half, Mitchell took command, scoring 16 points and knocking down four 3-pointers in the third quarter alone, including a buzzer-beater to give the Cavaliers a 90-78 lead heading into the fourth, when a frustrating night officially morphed into a rout.

Mitchell finished with 29 points on 10-of-19 shooting. All five Cleveland starters shot over 50 percent from the floor, with Max Strus the worst among them with five makes in 10 attempts.

Overall, the Cavaliers shot 54.7 percent from the field (47 of 86), and 46.4 percent from 3-point territory (13 of 28).

The Cavaliers made. And the Celtics? They missed, like the intent was not to make shots but damage the rim beyond repair.

All five Celtics starters were below the 50-percent threshold. Jayson Tatum and Jaylen Brown both went 7 for 17. Tatum was 2 of 5 from 3 and Brown 0 for 6.

Tatum, by the way, is now shooting 46 of 113 (40.7 percent) overall in the postseason, and 11 for 41 (26.8 percent) from 3. If he doesn’t get his shot straightened out in Cleveland, this vaults past a mere mini-slump into what’s-going-on-here? territory.

Unlike in Game 1, no Celtic could pick him up. Al Horford started fast, hitting three of his first four 3-point attempts before missing his last three from long distance and finishing 4 of 9 overall. Jrue Holiday was 2 of 7 — for such a valuable player, he sure has some weird shot charts — and even Derrick White was infected with brick-itis, making just 3 of 11 attempts.

The Celtics made an abysmal 33 of 80 field goal attempts (41.2 percent) and just eight 3s — or one fewer than White had himself in Game 1 — in 35 attempts (22.9 percent). The offense too often looked like some sort of bizarre tribute to Antoine Walker at his worst.

“We shot the ball both games that we lost here at home incredibly bad,’’ said Brown, referencing the Celtics’ Game 2 loss to the Heat in the first round, their only previous playoff loss until Wednesday. “And they shot the ball really well.”

But Brown did not leave it at that. Nor should he have.

“We didn’t play defense to our level tonight…Defensively, it was an unacceptable performance,’’ he said.

And that’s why what happened Thursday night can’t entirely be chalked up to Rivers’s familiar make-or-miss adage, and why we can’t declare this loss an outlier, which is what the Game 2 loss to the Heat turned out to be.

The Celtics’ recent history — not so much this season, but in the broader picture since Tatum and Brown settled in as the franchise cornerstones — suggests they don’t always handle prosperity well.

Complacency can return just when one starts believing it has been vanquished. They should be past the point of requiring a wakeup call or something alarming to happen, yet sometimes they still don’t wake up until smashing the snooze button a couple of times.

Maybe they got caught doing what we do: wondering what a showdown with the relentless Knicks would look like, or pondering whether the Timberwolves really are as ferocious as they look. Thinking ahead — daydreaming ahead — when there is still business, and the fearless Mitchell, to be overcome in the moment.

Celtics coach Joe Mazzulla didn’t parrot Rivers’s way of thinking, instead saying that poor spacing bogged down the offense and led to their woes in transition defense. He seemed to be trying very hard not to be too bothered by what he saw.

“You treat it the same way you would a win,’’ he said. “You come in tomorrow, watch the film, and you get better for Game 3.”

Maybe getting a few shots up wouldn’t hurt either, Coach. After Thursday’s debacle, this team could stand to see a few go through.