BOSTON — The work that 34-year-old Boston Celtics interim coach Joe Mazzulla put in before earning his first career win Tuesday night is something not too many head coaches — if any — can duplicate.

In preparation for his first NBA coaching clash on opening night — against Doc Rivers and the Philadelphia 76ers no less — Mazzulla left his home for shootaround at approximately 7 a.m. with the intention of not returning until late in the evening.

At the conclusion of shootaround, which officially started at 10 a.m., he drove straight to TD Garden, arriving at 12:30 p.m. From his office, he watched hours of additional film on the evening’s opponent.

And he even began looking ahead, choosing to dissect film of the Miami Heat, whom the Celtics play Friday.

Following film breakdown, he met with his coaching staff for some lighthearted fellowship. This is where trash-talking ensues, and it leads to the hardwood.

At 4 p.m., Mazzulla and his staff took the court to play some 4-on-4 basketball. They played for 45 minutes, and it was a physical set of games.

Mazzulla, a lefty, showcased a nice jumper.

They were going all out. There were hard screens set, forceful fouls unleashed, major pounding in the paint and, at one point, Mazzulla dove on the floor for a loose ball.

And this was all being done a few hours before tipoff.

Members of the Sixers’ coaching staff began to trickle in. They immediately noticed how the Celtics’ coaches were going at it, and the majority response was, “Damn.”

Drenched in sweat at the end of the games, Mazzulla went to freshen up to get ready for the real game.

Mazzulla playing pickup ball with the staff is something he’s always done since joining the Celtics in 2019. But he was an assistant in those years. He’s now the active head coach after the team suspended Ime Udoka for the entire 2022-23 season for a violation of workplace conduct.

Although Mazzulla is the youngest coach in the league, is actually playing a pregame ritual that can be executed 82 times before each game?

“It’s my therapy,” Mazzulla told Yahoo Sports. “It keeps me sane. It’s something I enjoy. I don’t take naps. This is how I unwind.”

He would later lead the Celtics to a 126-117 win. His team awarded him the game ball in the locker room.

A lot of work was put in by Mazzulla before the victory, but the humble coach is quick to pass the credit and acknowledge his shortcomings.

It’s one of the main reasons why it’s been such a seamless transition for the organization.

“Right now, I have to rely on my players. They are currently better at their job than I am at my job,” Mazzulla told Yahoo Sports. “It’s going to be a learning experience for me. But we’re going to do this together and I’m going to get better. I look forward to what we can accomplish as a group.”