Joe Mazzulla has been a head coach before. He was a head coach for two seasons at Division II Fairmont State, located 20 miles south of Morgantown on I-79.

He was also in charge of the Boston Celtics NBA Summer League team in 2021.

But until Sunday, Mazzulla had not been an NBA head coach for a game played during the league year.

That changed when he stepped onto the parquet floor in Boston Sunday afternoon for the Celtics’ preseason opener versus the Charlotte Hornets.

Mazzulla and the Celtics cruised to a 134-93 victory, giving the 34-year-old his first professional head coaching victory.

“It felt like I was coaching a great team that wanted to win,” Mazzulla told reporters. “That was fun to coach. Just grateful for it. Like I said, grateful because the Celtics, grateful because I get to coach a bunch of great guys and great players. And not many people in my position get that opportunity, so just really being more grateful than anything.”

Mazzulla appeared to push all the right buttons in his head coaching debut.

Boston shot 57 percent from the floor, and made nearly 47 percent of its shots from beyond the arc. The Celtics led by as many as 46 points, and dished out 41 assists in the contest.

“They want to play the right way,” Mazzulla said. “They had good intentions.”

The former Mountaineer guard was thrust into the interim head coach role last month amid an investigation into Boston head coach Ime Udoka, who was suspended for the entire 2022-23 season.

Mazzulla called this season a “great opportunity” for himself and the Celtics organization. Boston is coming off of a trip to the NBA Finals.

Mazzulla, who has already received the backing of team President Brad Stevens and others, was complimented by the Celtics’ biggest offseason acquisition.

“He’s very deliberate, very direct. He’s not a guy that’s gonna overtalk you and tell you too much, because he wants you to go out and have a clear mind,” said 2017 NBA Rookie of the Year, guard Malcolm Brogdon. “He’s going to be very direct and very honest with what he expects from you, which is I think everything an NBA player wants in a coach.”

Boston begins the regular season on Tuesday, Oct. 18. The game will be nationally televised on TNT.