In a candid, eye-opening interview, Boston Celtics assistant coach Sam Cassell has pulled back the curtain on the relentless drive, culture, and adaptability that are powering this Celtics team through massive upheaval — turning doubters into believers as they sit second in the Eastern Conference heading out of the All-Star break.
The numbers tell part of the story: second-best offensive rating in the NBA, opponents held to the second-fewest points per game, and a third-ranked net rating. The Celtics have every hallmark of a legitimate title contender.
Yet this level of success was far from what most outsiders expected after the departure of key championship-core pieces, the exits of front-office fixtures Austin Ainge and Remy Cofield, and Jayson Tatum’s ongoing rehab from a torn Achilles. For all the change, the team’s identity, culture, and work ethic have never wavered.
“People just counted us out,” Sam Cassell said in an interview lightly edited for clarity and grammar. “We’re just a hard group, a hard group of guys playing basketball, coaching a game of basketball, we’re together as a unit. Our staff is wonderful. Our players are wonderful. Our players allow us to coach them hard, and the result they’re getting is because they’re driven, and they allow us to coach them the way we coach them.”
Cassell stressed that total buy-in to individual roles is non-negotiable. Moving from lifelong star status to contributing primarily through defense, rebounding, or facilitation is never easy — but it’s exactly what championship teams require.
“Our guys, they don’t want to just be the stars of the NBA,” he conveyed. “They just want to be good players in the NBA. The best team in the NBA, and teams, don’t just come from who’s scoring all the points. It takes a team to win one NBA game, and I think we have a pretty good team that we understand how we have got to win and what we have to do to win.”
Adapt or get left behind
Losing Jrue Holiday, Kristaps Porzingis, Al Horford, and Luke Kornet raised the stakes dramatically. The Celtics didn’t just have to replace talent — they had to evolve with the league’s direction and squeeze every ounce of potential from their new roster.
Understanding they needed to play faster, Boston has flipped the script: after ranking last in average offensive speed a season ago, they have significantly increased their tempo this year, per NBA.com.
“We have to play faster because the league is turning that way, and we don’t want to be the team that’s left out,” stated Cassell.
The staff also solved the challenge of no longer leaning on Tatum-centric pick-and-rolls that exploited switches. The new identity is a fluid, multi-option, read-and-react offense that perfectly suits the current group.
“You always have to have an understanding of where the league is heading,” Joe Mazzulla said in late November. “And I think the league is heading — just playing, as you can see, playing at such a faster pace. I also think with the physicality, the effort defensively, I think a lot of teams are adjusting more on the fly of, like, you’re never going to see the same possession, same coverage, 2,3,4, plays in a row. And so, going to a faster pace, a read-oriented thing, a little bit more of that, it matches our personnel. But it’s also, I think, kind of where the league is headed.”
The roster refresh has given hungry players — Jaylen Brown, Jordan Walsh, Baylor Scheierman, Neemias Queta, Luka Garza, and others — the biggest stage of their careers to prove themselves. That hunger has produced a non-stop, relentless effort that has become the Celtics’ signature trait.
“We compete,” Cassell voiced. “We did, we competed the last two years, but we understood that we were so talented the last two season that, some days we didn’t compete. We still won games that we really didn’t compete in. So, we were that good, but we understand that we are good, but we have to compete as much as possible for us to win.
“I think our guys, from 1 to 10, have bought into that system and they enjoy the system, and on the days we do compete, and we lose, we know, we just — we commend the other team and get better for the next game.”
What makes Joe Mazzulla special
Joe Mazzulla’s work this season has placed him firmly in the Coach of the Year conversation — currently sitting in the top three in betting odds. In the opinion of many, including this writer, his case is the strongest.
The entire Celtics coaching staff has completely reshaped how the team plays on both ends of the floor, maximizing a new-look roster and keeping Boston in the title hunt despite losing five rotation staples, including Tatum.
What stands out most to Cassell about Mazzulla’s leadership?
“He’s an awesome communicator. He doesn’t pretend to have all the answers to all of the problems. That’s the best thing about him,” said Cassell. “Being an assistant coach on his staff, I understand that if there’s something that he doesn’t know or understand about, he will ask; it doesn’t matter who on the staff, he will ask. And that’s a sign of a good leader in my eyes.
“He understands what it’s going to take for us to win every night. And if we don’t have one ingredient that night, he may be pissed, or I may be pissed, but we get over it and try to get better for the next game. It’s always the next game, you know, it’s always the next game with us. We want to compete for 48 minutes, and that’s the makeup of our team. We want to compete.”
Beyond tactics, Mazzulla shows real care — supporting Tatum through rehab, visiting Queta at Utah State in the offseason, attending Chris Boucher’s baptism in Montreal. Those genuine relationships create the trust needed to push players to their limits.
“It’s just like any other thing. It just takes time. It takes trust,” said Cassell. “Trust comes from two sides; it comes from the players’ side, and it comes from the coaching side. When a coach and a player have a mutual respect for each other, a player might not want to hear what the coach has to say all the time, but he respects it, and he’ll listen to it.”
Sam Cassell’s head coaching pursuit
After 15 years as an elite floor general and 17 seasons as an NBA assistant, Cassell has mentored stars from John Wall and Shai Gilgeous-Alexander to Tyrese Maxey and Jayson Tatum. He helped deliver Banner 18 and is now orchestrating one of the most impressive turnaround stories in recent memory.
He has paid every due, yet a head-coaching opportunity — in the NBA or even at his alma mater Florida State — has not yet arrived. Cassell refuses to give up.
“God is good,” he says. “You know what I’m saying? So I’m not giving up. Hopefully, it happens for me. I would like to have an opportunity to coach one of these teams, but the enjoyment I get from being a coach in basketball is seeing young men, when they are first getting in the league, and their progress in life is becoming good basketball players, becoming family men, and becoming fathers. That’s the part I enjoy.
“The coaching thing, I would love to have an opportunity to do it. I’m striving for it because I still love this. I wouldn’t do it if I didn’t love it at all. I love this. I love what I’m doing. I always have a smile on my face. I’m just upbeat. I enjoy being a part of the Association, especially being part of the Boston Celtics.”
That passion, that culture, and that unbreakable trust — the very things Sam Cassell just laid bare — are exactly why these “counted-out” Celtics remain one of the most dangerous teams in the NBA.