BOSTON—When Boston Celtics guard Derrick White stood in the corner behind the 3-point line late in Game 4 of the NBA Eastern Conference finals as teammate Jaylen Brown drove into the lane, drew defenders, and flipped a pass toward him, White felt prepared for the moment.
That’s because Celtics Coach Joe Mazzulla had simulated scenarios just like it throughout the season.
“It starts in practice with them championship stations that Joe loves to do,” White recalled. “It starts there, and then just continue to trust one another.”
White trusted that Brown would make the correct basketball play. He did, and it ended with White connecting on a tie-breaking 3 that ultimately secured Boston’s place in the NBA Finals and a matchup with the Dallas Mavericks.
The play may also be a perfect example of how in his second year as coach, Mr. Mazzulla has managed to help the Celtics recover from the disappointment of a season that ended on the cusp of the Finals a year ago, to a run this season that again has them four wins away from capturing the franchise’s 18th championship.
White’s shot, Mr. Mazzulla said, is a microcosm of the kind of a team culture he’s tried to cultivate over the past two years. One that puts details first.
“Things that you can’t take for granted,” said Mr. Mazzulla, who at age 35, is the youngest head coach to reach the NBA Finals since Boston’s Bill Russell (also 35) in 1969. “Sometimes it’s as small as getting the ball inbounds. But just try to pick little things, that we see on a nightly basis, that can impact winning and can affect losing. And we just practice them over, over, and over again until they become second nature.”
What’s become equally central to the Celtics’ success this season is the buy-in to an egoless, team-first philosophy in which individual credit is secondary on a roster loaded with current and past all-stars Jayson Tatum, Jaylen Brown, and Jrue Holiday, along with White, 7-footer Kristaps Porzingis, and a deep bench.
Meanwhile, Mr. Mazzulla has also benefited from working alongside a coaching staff he was able to choose this offseason. That’s something he didn’t have last season after being thrust into a job he didn’t expect to have following predecessor Ime Udoka’s suspension just days before the start of training camp.
Lead assistant Charles Lee and Sam Cassell have helped Mr. Mazzulla tweak a system built around 3-point shooting and defense, which saw the Celtics rank first and third, respectively, in offensive and defensive rating during the regular season.
Those rankings have remained the same this postseason for a team that is 6–0 on the road and 3–0 in close-out games.
But as much as Mr. Mazzulla and his staff have driven home their philosophies via X’s and O’s, they’ve also continued to focus on the mental aspects of the game.
Last season, it was in film sessions that began with Mr. Mazzulla showing the team images of sandcastles, which he used as a metaphor that even the best castles get washed away by the daily tide—requiring them to be rebuilt.
It was something Tatum said was “a little cheesy,” but “something we bought into.”
Mr. Mazzulla’s tactics were on display again during a blowout win over Phoenix in March. He went viral after he sprinted to contest the Suns’ Royce O’Neale’s practice basket heading into a timeout.
“I saw a guy going in to get a shot and he hadn’t made one, and I didn’t want him to feel good about himself going to the bench,” Mr. Mazzulla explained at the time. “That’s the bench rule. ... If I’m going to ask the guys to contest, staff’s going to do the same thing.”
Mr. Mazzulla said later during an appearance on Boston radio’s 98.8 that instances like that are the foundation of their team culture.
“We can laugh about it. But at the end of the day, I think you have small moments in your organization to set the temperature of what you want to be about,” Mr. Mazzulla said. “We did that last year, and thinking back, that’s an important thing, that mindset that we try to bring. That we’re going to bring it every day. That we want our opponents to constantly be uncomfortable. We don’t want to give them an edge at any point.”
Holiday acknowledged that Mr. Mazzulla’s style is unique, but one that he’s come to appreciate during his first season in Boston.
“You go with it. You go with the craziness,” Holiday said. “I think maybe it’s controlled madness. I think it’s definitely his way of preparing us, and I feel like preparing himself. And I feel like it’s been working. It’s fun. It’s different. ... Joe definitely brings a spark and some weird energy.”
From Mr. Mazzulla’s perspective, it’s about forming the kind of bonds that may ultimately bring Boston another championship.
“I think one of the best gifts, things that I have, is why I got into coaching, building relationships with guys,” he said. “When I left college to go to the NBA, most people were, like, hesitant about that because NBA guys get a negative rap as to being able to build relationships with them. But I felt like it was, ‘There’s a lot there.’”
