When the Boston Celtics acquired Kristaps Porzingis and Jrue Holiday ahead of the 2023-24 season, they were left with a six-man rotation and an unproven bench.

Boston Celtics head coach Joe Mazzulla. David Butler II-Imagn Images

In the previous season, Payton Pritchard (16.1), Sam Hauser (13.4) and Luke Kornet (11.7) had all averaged less than 20 minutes a game for a combined production of 15.8 points.

At the time, many analysts felt Boston needed to add bench depth to ease the workload on the six-man crew of Jayson Tatum, Jaylen Brown, Derrick White, Al Horford, Porzingis and Holiday.

Celtics head coach Joe Mazzulla had a different plan in mind. He decided to look inward and place his faith in Pritchard, Hauser and Kornet.

Under Mazzulla, all three took significant strides last season, playing key roles in Boston’s run to the championship.

This season, they’ve turned into a three-man wrecking crew off the bench, with Pritchard emerging as the frontrunner to win Sixth Man of the Year. Last week, Pritchard and White became the first pair of Celtics to each score 40 in a game.

On Monday, Hauser had himself a career night, going off for 33 points in Boston’s 114-108 win over Utah. The sharpshooter also broke a franchise record for threes in a quarter.

It’s remarkable that Pritchard and Hauser, a pair of unproven players 18 months ago, are now setting franchise benchmarks for the C’s. Much of the credit goes to Mazzulla, who has unlocked their talents with his “let it rip” philosophy on three-pointers.

After Pritchard’s career night last week, ESPN’s Brian Windhorst broke down the role Mazzulla played in his career growth.

“Payton Pritchard is the demonstration of the Joe Mazzulla system,” Windhorst said on “Get Up” on ESPN. “When Joe Mazzulla became the head coach, Payton Pritchard was barely playing. His confidence was shaken and Joe Mazzulla said, ‘Guys, I don’t care if you’re 0-10, keep shooting threes.’”

Pritchard heeded Mazzulla’s words and kept shooting. This season, he ranks No. 7 in the league with 210 threes in 64 games.

With Prichard, Hauser and Kornet turning into high-caliber bench players, the Celtics now have a quality nine-man rotation entering the playoffs. Even Neemias Queta and Torrey Craig can provide good minutes if need be.

The depth has also allowed the Celtics to keep their starters fresh ahead of their upcoming NBA title defense. It’s an ominous sign for the rest of the league.