BOSTON — A scandal off the court cast a shadow over the Boston Celtics entering the preseason.

On the court, they opened the regular season looking like a team still very much capable of contending for a championship.

Jayson Tatum and Jaylen Brown each scored 35 points and the Celtics beat the Philadelphia 76ers 126-117 on Tuesday night in the NBA’s season opener.

Malcolm Brogdon added 16 points and Grant Williams finished with 15 as the defending Eastern Conference champions gave interim coach Joe Mazzulla a victory in his debut on a night the team honored the legacy of Bill Russell.

“It was just unique and special,” Brown said. “It feels a little bit better knowing who we were playing and who we were playing for.”

Mazzulla has been tasked with leading the team after Ime Udoka was suspended for the season following an investigation by a law firm that found he committed multiple violations of team policies.

Mazzulla successfully led a Celtics team that very much resembled the one that made a surprise run to the NBA Finals a season ago.

“It was a proud moment,” Mazzulla said. “I think at the end of the game, the ‘Let’s go Celtics! ‘chant — we picked up right where we left off. … When they’re cheering for you, you’re doing something right.”

Boston opened up a 110-97 lead with 8 minutes to play and never trailed again.

James Harden scored 35 points — his most since joining the 76ers last season — including 12 of 12 from the free throw line. He also had five 3-pointers.

“We gave them 20-plus points in transition,” Harden said. “That’s the game right there.”

Joel Embiid added 26 points and 15 rebounds. Tyrese Maxey finished with 21 points.

Mazzulla has vowed to keep the focus on building upon the culture Udoka established on the court as a rookie head coach last season.

He insists that it will be done primarily on the defensive end of the floor, but the offense was the story for the Celtics on Tuesday with 56% shooting from the field.

With big man Robert Williams sidelined as he recovers from offseason surgery on his knee, the Celtics stuck with the same starting lineup they employed during the preseason, playing defensive stalwart Derrick White alongside Marcus Smart, Tatum, Brown and Al Horford.

The smaller group sped Philadelphia up at times, forcing the 76ers into 14 turnovers for the game, leading to 22 Boston points.

The 76ers are looking to contend with the top teams in the East with Harden embarking on his first full season in Philadelphia after being swapped for Ben Simmons late last season in a trade with Brooklyn.

Harden looked rejuvenated coming off a season defined by hamstring injuries that hampered his effectiveness in a truncated 21 regular-season games with the Sixers last season.

The 10-time All-Star frustrated the Celtics, displaying the mobility he was missing a year ago. He was able to get to the free throw line often. He also was effective from the 3-point line, connecting on four in the first half, including a rainbow heave from the top of the key to beat the shot clock late in the second quarter.

TIP-INS

76ers: Were outrebounded 36-31. … Led 29-24 at the end of the first quarter, with Harden scoring 16 points in the period and going 8 of 8 from the free throw line.

Celtics: Outscored the 76ers 24-2 in fast-break points. … Shot 71% in the second quarter with no turnovers. … Opened game on 9-2 run before being outscored 27-15 the rest of the quarter.

GETTING HEATED

Tempers flared briefly in the third quarter when Smart took issue with Embiid holding onto his arm and then standing over him following a rebound. Smart got up and pushed Embiid, leading to a brief scrum between the teams.

Smart said he felt Embiid tried to break his arm.

Following a review by referees, Smart was assessed both personal and technical fouls.

“I could have cracked his head open, but I didn’t,” Smart said.

Said Embiid: “”It’s basketball. Emotions. The first game of the season. Rivalry, Boston-Philly.”

HONORING RUSSELL

The Celtics held the first of two planned ceremonies this season to commemorate the life and legacy of Bill Russell, who he died July 31 at age 88.

There were video tributes highlighting some of Russell’s biggest moments on and off the court.

The team also wore No. 6 patches on its special edition jerseys. The uniforms included 11 gold diamonds down the sides, signifying the 11 championships Russell helped bring Boston during his career.

His widow, Jeannine Russell, sat courtside and tearfully acknowledged a standing ovation from fans during a timeout in the third quarter.

UP NEXT

76ers: Host Milwaukee on Thursday.

Celtics: Open a three-game road trip Friday at Miami.