BOSTON — Joe Mazzulla has been so steady guiding the Celtics through a franchise-shaking crisis that their turbulent offseason has taken a back seat to their championship aspirations.

The team rewarded him by turning a temporary opportunity of a lifetime into a permanent one.

Boston named Mazzulla its full-time head coach on Thursday, removing the interim tag he had held since stepping in for Ime Udoka in the preseason.

Udoka initially was given a yearlong suspension before training camp for having an inappropriate relationship with a woman in the organization. The 34-year-old Mazzulla, previously an assistant under Udoka, will now replace his former boss, who is no longer with the team. Mazzulla is the NBA’s youngest head coach.

“Since I’ve been here I always knew where I stood,” Mazzulla said Thursday. “And even though it was an interim position … I knew I was going to get a fair shake and get an opportunity. I knew I was going to be able to do it the way that I thought to give us the best chance to be successful without any pressure because of that.”

Terms of his new deal were not released, but the team said his promotion includes a contract extension.

“I’ve always been surrounded by great people and great coaches,” Mazzulla said. “I just think I’m a byproduct of all the different environments I’ve been in.”

Mazzulla’s Celtics have the best record in the NBA (42-17) and led Milwaukee by one game in the Eastern Conference ahead of the Bucks’ game at Chicago on Thursday night. Boston won’t play again until after the All-Star break.

Mazzulla said he found out the process of making him the permanent coach was underway two days ago and that the deal was finalized after the Celtics’ 127-109 win over Detroit on Wednesday.

Mazzulla and his assistants will coach Team Giannis – the team that will be captained by Milwaukee’s Giannis Antetokounmpo – in the All-Star Game on Sunday at Salt Lake City. Boston’s Jayson Tatum and Jaylen Brown were named All-Stars.

“One of the things that’s pretty obvious and evident about Joe is he’s a really good coach and he also is just an outstanding leader,” Celtics president of basketball operations Brad Stevens said. “I think he’s done a great job right from the get-go of galvanizing the locker room around a mission.”

Stevens said he decided to elevate Mazzulla now because of the job he’s done and because he didn’t want the coach and his staff to enter the second half of the season under “a cloud of uncertainty.”

“They’ve certainly have earned that,” Stevens said.

He declined to elaborate on why he made the move now instead of waiting until the season ended.

“We said in our original statement long ago that the decision would be made at a later date. We wanted to make sure we were thorough, we were really focused on our team from that day on,” Stevens said. “I thought the players’ leadership, the staff’s leadership and Joe’s leadership have all stood out during that time.”

Mazzulla, who is from Johnston, Rhode Island, was recognized as the Eastern Conference Coach of the Month for games played in October and November after leading the team to a league-best 18-4 record (.818).

He said being on top of the East is something he would take the time to appreciate over the All-Star break – while also thinking about how the Celtics can maintain their strong play in the second half.

“It’s there, you can’t run away, you can’t ignore it,” Mazzulla said. “I do think there is a comfort level knowing that. But that was kind of my message to the guys. That at the same time you can’t be too comfortable because when we get back, it picks right up.”

Udoka, a longtime assistant, led Boston to a 51-31 record last season, his first as a head coach – going 26-6 in the final 32 games. The Celtics then beat Brooklyn, Milwaukee and Miami on the way to the NBA Finals, where they lost to the Golden State Warriors in six games.

Before training camp, the Celtics banned Udoka for a full season over what two people with knowledge of the matter said was an improper relationship with a member of the organization. The people spoke to The Associated Press on condition of anonymity because the team did not reveal that detail publicly.

Despite those circumstances, Boston looks fully capable of winning a title.

“All things considered, everything that we’ve went through this season as a team with coaching changes and guys getting injured, missing games and being in and out of the lineup. … Overall, it’s been a hell of a start,” Tatum said after the win over Detroit.