Sam Cassell, who won an NBA title with the Celtics, is joining the coaching staff in Boston after spending the last 10 years as an assistant with Doc Rivers. Ralph Freso/Associated Press

LAS VEGAS — The Celtics’ coaching staff will be seeing plenty of new faces this year amid a busy offseason as Coach Joe Mazzulla prepares for his second season, and none will be as notable as Sam Cassell. The three-time NBA champion has spent much of the past decade as an assistant coach under Doc Rivers and was looking for a new opportunity after Rivers was dismissed by the 76ers.

“Right after the playoffs was over, we got together, couple phone conversations,” Cassell said of his talks with Mazzulla. “Asked me if first of all, if I was interested in coming here, join his staff, the Celtics, I just told him it’d be an honor. I hadn’t heard from anybody else. It was an opportunity that I was looking forward to. I think Joe’s an amazing coach. I’m here to just help him just let him enjoy that we have a great team. I won’t change his mentality, that’s who he is. But I’m going to help him enjoy it a little bit more.”

Cassell along with former Bucks top assistant Charles Lee will become Mazzulla’s right-hand men on a reworked bench. Several of Ime Udoka’s former assistants have joined him in Houston so there were important gaps that needed to be filled.

Cassell will bring a unique perspective as a longtime NBA player along with his lengthy coaching experience and he plans to use that knowledge to his advantage.

“I’ve been, as a player, I’ve been every player from the best player to the 15th man on the team,” Cassell said. “I know how each player feels so I can relate to each and every one of them. The guy who gets the ball all the time, the guy who doesn’t get the ball. I won a championship in Boston and I was maybe the eighth or ninth man. Some nights I played, some nights I didn’t play but I was always in the game plan and that’s my message to them. You got to be in the game plan, you got to be in the moment to seize the moment.”

With Boston losing a pair of key chemistry pieces this offseason in Marcus Smart and Grant Williams, Cassell is taking it upon himself to make sure Boston’s stars find a new level to bring a championship to Boston.

“Both guys, they want to be great,” Cassell said of Jayson Tatum and Jaylen Brown. “They are pretty great basketball players. But just being good don’t cut it. Understanding what winning a championship in Boston is about, man, that’s the part that can be a motivation for both of them. But it’s not just going to be them two. This is a team game. This is a team sport. Even guys from the top down to the 15th man, we all gotta click and be together. That’s why I know I’m great at, just stay in the moment, getting guys to stay in the moment. Stay in the moment means if you’re playing five minutes, it’s going to be the best five minutes, the hardest five minutes you’ve played in your life. That’s the key right there.”

The former Celtics champion will also provide a tough love mentality during what will be a pivotal year for the franchise.

“These guys got so many other things besides basketball in their lives,” Cassell said. “I think the balance I’m going to bring is to have that balance. You can’t be the answer to the world crisis but you can impact the world with your voice. The whole main thing is winning Banner 18. That’s the only thing that matters to me and if it matters to me, I’ll make sure it matters to them.”

GRIZZLIES: The future of a lawsuit accusing Memphis Grizzlies star Ja Morant of assaulting a teenager during a pickup basketball game hinges on whether Morant will be allowed to say that he was acting in self-defense and can receive immunity under Tennessee law.

A judge on Wednesday ruled that Morant’s lawyers can proceed for now with their argument that Morant was acting in self-defense when he punched Joshua Holloway during a game at the All-Star player’s Memphis-area home in July 2022.

Morant’s lawyers have acknowledged he punched Holloway one time after Holloway threw a basketball at Morant and the ball hit Morant in the chin. In a July 26 motion, the player’s lawyers said he should be immune from liability under the state’s “stand your ground” law, which allows people who feel threatened at their homes to act with force in certain situations.

Circuit Court Judge Carol Chumney said the next step would be to hear from lawyers in the case, including those representing the Tennessee Attorney General, about whether the law can be applied to the case under the state Constitution.

Morant’s accuser was 17 when the lawsuit was filed. It accuses Morant and friend Davonte Pack of assault, reckless endangerment, abuse or neglect, and infliction of emotional distress. An amended complaint identified the plaintiff as Holloway, who is now 18.