Joe Mazzulla loved soccer growing up in Rhode Island. The free-flowing run of play and nature of the formations made it a canvas to paint sporting creativity.

Though he pursued basketball, soccer never left him. When he got to West Virginia for college, he knew he was far from the most talented basketball player in the Big East. But he was able to translate the footwork, conditioning and reads to the court, which helped carry his team to a Final Four.

More than a decade later, he worked his way to the Celtics bench, first as an assistant coach. He had his own ideas for how to run a club, but he figured it would be a few years before he was the one holding the clipboard.

Then Ime Udoka was let go, Mazzulla leapfrogged to the top job, and conveying his vision became a priority. So what did he do?

He put on a Manchester City match for the Celtics. He explained the philosophies that have made their manager, Pep Guardiola, one of the sport’s best.

He showed his team that, like soccer, basketball is a continuum.

“That is what the game of basketball is about, to me, and what counterattacking in soccer is about,” Mazzulla told The Athletic. “So I study a lot of Man City. I study Pep a lot. I think he’s the best coach at any level, in any sport. It’s had a huge influence (on me).”

Mazzulla wanted to slowly challenge the idea that offense and defense exist on their own planes. Over the past decade, both basketball and soccer have grown more into transition sports valuing versatility.

The Celtics coach embraced making every play more improvisational, where everyone on the floor can do a little bit of everything. The game became more about finding small advantages and pursuing them. But that meant understanding how an advantage came to be.

When you see a big man posting up a smaller guy on one end, it starts with how the previous possession ended. It’s all one cycle.

“Everybody tries to break basketball up into offense and defense, but it’s one game,” Mazzulla said. “If your transition defense sucks, everybody talks about your transition defense. But it’s your spacing and your decision-making and your shot selection, then it’s your transition defense. I think where basketball and soccer are the same is the transition is happening so fast. You can be on offense and two seconds later, you can be on defense. So the game is constantly changing.”

Mazzulla boils down the overlap between basketball and soccer to playing one-on-one in a closeout situation. The game is about negotiating the angles to get past a player or keep a player in front of you, depending on which side of the ball you’re on at that moment.

In the modern version of both sports, you’re switching between doing both constantly and your success on one end is often dependent on the other.

“To me, regardless of the sport, it could be lacrosse, soccer or basketball; those one-on-one situations, all fundamentals are the same,” Mazzulla said.

The question for Mazzulla was whether he could get his players to understand and embrace this vision. So he had to find a way to communicate in a way that both introduced them to his thought process while showing how it translated on the court.

“Soccer and basketball, when I watch it, it’s kind of the same sport from that tactical standpoint of how do you create advantages?” Mazzulla said. “How do you create two-on-ones? How do you recognize weaknesses in the defense and how do you take advantage of angles?”

For Al Horford, this wasn’t an entirely novel concept. He’s a Premier League fan as well. He’s been watching soccer long before the rest of his teammates, and in his prime, Horford ran the offense from the perimeter.

But he was playing on teams with more distinct roles across the lineup. This new “Mazzullaball” removed the silos between roles on each end of the floor.

“Even myself, I’m learning from him just how he is making us understand how to work and take care of those advantages. That’s what he calls them,” Horford told The Athletic. “He wants us to see and execute and really not just be robots out there. Whatever the game is dictating, do it.”

One of Mazzulla’s favorite drills at practice consists of two five-man lineups walking onto the court with no offense/defense assignment. Then he throws the ball to one group and everyone has to jump into the right play call and defensive coverage immediately.

No time to think about what you’re going to do. Immediate read and react.

“It rewires your brain to transition,” Mazzulla said.

This framework revolves around a core principle: Read fast, play slow.

“It’s made me a more efficient basketball player, just because you need to make the game easier for yourself,” Jaylen Brown said. “I feel like I can score with the best of them on anybody. But when you are identifying and manipulating the game and getting the right matchups on you, playing slow, taking your time, those are easier baskets.”

What Brown had to learn was that it wasn’t about creating easier baskets for himself. It was about creating easier baskets for the team as a whole. If he could focus on doing that, then the opportunities to score would organically come his way.

Brown has found the balance between forcing himself into the game when he senses the need and feeling comfortable sitting back.

“Then they start doubling. You want to double? OK, I’m gonna drag the double out and make the right play and our team is going to get open looks,” Brown said. “Just making the game, thinking the game, manipulating the game is all about what we’ve been emphasizing this year.”

GM Brad Stevens and the front office made moves last summer to fit Mazzulla’s vision. Kristaps Porziņģis gives them the ability to target cross-matches whenever he is on the floor. Jrue Holiday can play any position at any time and has no problem being away from the ball.

This roster has given Mazzulla the creative freedom he relishes. The result is a 7.5-game lead in the East and a 10.5 net rating, tied for the ninth-highest in NBA history with the 1971-72 Lakers.

“That’s probably my favorite part about the job, is looking at it from an artistic perspective,” Mazzulla said. “(It’s) giving the guys a framework to be like, there’s so many possibilities here. Let’s explore them.”

Joe Mazzulla has become more comfortable with his vision in his second season with the Celtics. (Maddie Meyer / Getty Images)

Mazzulla fared well in his first season inheriting the blueprint Udoka laid out. It utilized Rob Williams’ energy to keep the floor spaced, but that roster didn’t quite fit Mazzulla’s principles.

Williams was an active screener and a menace in the dunker spot whose presence afforded driving lanes for his teammates and provided a safeguard if they couldn’t score themselves. But Mazzulla wanted to build a more flexible system, a scheme that reimagined the five-out offense while still pressuring the middle of the floor.

“A closed-minded approach is where you get into stagnation,” Mazzulla said. “It’s not like we were closed-minded, but (we had a) rigidity of doing it a certain way.”

Half a decade ago, teams were abandoning the post because some coaches felt it was inefficient and slowed down the game. But as the league continued to prioritize defensive versatility and switching became the norm, finding mismatches and bringing them to the post became easier. The Celtics saw where that curve was trending and Stevens gave Mazzulla the talent last summer to capitalize.

Now the Celtics’ system is almost designed around the post-up. Get the mismatch, take them to the post, and then wait to see if the double comes.

But Mazzulla doesn’t even call them mismatches. That word implies that it’s a mistake for someone like a guard to end up on Porziņģis or a big to be marking Derrick White. But teams are switching the Celtics, knowing what Mazzulla is trying to do.

That’s why he labels it a cross-match. His offense is designed to survey the defense, ask what it wants to do, and then do what the defense is trying to avoid.

Opponents only have a few seconds in transition to get the matchups they want on the Celtics. If they don’t, Boston has an action for every possibility. Even though it seems simple, it works because they’re coordinated, consistent and clever.

However, it only works if Mazzulla has done most of the work before the game. It ties back to Guardiola, who brought tiki-taka to the forefront with Barcelona. Tiki-taka is built on quick, constant passes back and forth until the defense is compromised enough to attack an opening.

For Mazzulla, it was the visualization of how a coach manages the game so differently in soccer.

“That’s where my timeout philosophy started. I think soccer coaches are the best teachers, because once the game starts, you can’t call a timeout,” Mazzulla said. “The ability to create a system where your guys can operate and function based on the ebbs and flows of the game and how the game is going is really important. You have to empower your players to understand exactly how the game’s going and how quickly you can self-correct to either stop a run or create your own run.”

So as Mazzulla brings his team into the film room and the Celtics pour over the dozen or so possessions from the prior game he wants to recreate or improve in the future, he will tie it back to the soccer fundamentals. Get the ball to the advantage wherever on the floor you can find it and move from there.

“Pep, his style, it’s like that same Barcelona style, getting everybody involved, getting everybody touching the ball,” Horford said. “I feel like every couple games, Joe’s showing clips to us of possessions where everybody’s touching it and how the ball has energy. When the ball is moving and everybody’s touching it, something good is happening. That’s when we’re playing at our best.”

Mazzulla said he enjoys confrontation. He’s tried to build a work climate where competition is allowed to flourish in a safe space.

But it took a season for that to work. Maybe it was the assurance that comes with surviving that first year as a head coach or having a full offseason to understand how he wants to present himself, but he feels like he is finally being his true self.

His players see that and are fully embracing his ways.

“They know me now because I’m the same way all the time,” Mazzulla said. “I’m not perfect by any means, but I’m very rarely inconsistent in how I approach communication, how I approach practice, how I approach the game, my humor. I use humor if you win, I use it if we lose. I don’t take myself too seriously most of the time. If I have to tell you the truth versus if I have to listen, I try to just be consistent. And I think that gives me the space to do that.”

GO DEEPER

Celtics’ Joe Mazzulla welcomes external noise, even if it’s loud: ‘It’s beautiful’

He also needed time to slowly show everyone around him how he operates. He still sees himself as a kid from Rhode Island, where talking trash is a love language.

So in his first season, he struggled to show his brash but empathetic personality, oscillating between defensive and quiet in a way that often added to the tension.

“I probably strayed from doing that a little bit because I was figuring out how I was going to be myself,” Mazzulla said. “I was like, I can’t just come out and be myself fully, because nobody would understand it. I had to give it time.”

Last year, the public saw an awkward and hesitant unveiling of Mazzulla’s persona. Bits of the sarcastic edginess were present, but they were presented without the familiarity needed for it to make sense to many in the media and fans alike.

“I think if you look at my relationship with the media now, to me, it’s having fun,” Mazzulla said. “I grew up like, if I bust your chops, if I’m going back and forth, I really like you guys. I’m having a good time. It doesn’t mean anything other than let’s get in the octagon. It’s the ultimate compliment. It’s not even messing with people.”

Now that Mazzulla is less guarded, he said he sees his press conferences as five minutes where he and the media have to sit together, so they might as well have a good time.

He no longer feels the need to bury his personality.

“I haven’t done that (this year). I felt like I had to do that last year. I feel you got to earn it. You got to earn the right to show your personality as a coach,” Mazzulla said. “You can’t just come out and just do whatever the hell you want. That’s how I look at it. So I felt like there were times where, like last year, I had to be guarded. But then I also had to be like I got to earn doing this. When I was like, ‘This ain’t a country club,’ you have to earn the right to say that. But that’s what I would say 10 times out of 1o.”

While it’s been a journey finding his voice publicly, Mazzulla has felt like the organization has given him the freedom to be himself. It’s just taken a while for him to realize what that means as the head coach of one of the NBA’s biggest franchises.

He sees alignment from ownership to the coaches to the players and calls it, “the ultimate gift.” He said it was hard for him to appreciate it last season because he was so occupied with winning in the regular season and playoffs. It wasn’t until the Celtics were eliminated that he said he found clarity.

“You take a look at last year and just everything you go through, it wasn’t a life or death situation,” Mazzulla said. “It was just a difficult adjustment in Year 1 of being a coach. But if you achieve what we achieved as a team and you get to where we get to, when you go through the things that we do, it’s a surrender to, ‘We did what we did and it wasn’t good enough.’

“That’s a compliment. I find peace in that.”

He knows he can’t stop learning and growing. While his players were away, Mazzulla spent his All-Star break in  Manchester, finally getting a chance to meet Guardiola and learn up close.

He wanted to see what success in the Premier League looked like from the moment you walked through the door. Mazzulla can see the principles in action when he puts on a City match. He can watch Guardiola’s interviews to understand how he thinks the game. But he had to see it up close, and Mazzulla was able to soak it all in while he was there.

“You get an environment of what greatness is like and I’d say they’re pretty close to greatness with what they’ve done over the last nine years and what he’s done at Barcelona,” said Mazzulla.

“It’s just good to be around that, study that, learn from it.”

(Top photo: Tim Nwachukwu, Catherine Ivill/Getty Images)