Tyrese Maxey didn’t expect Game 1 of his team’s first-round playoff series to be that noncompetitive.

The Celtics, heavily favored as the No. 2 seed in the Eastern Conference, battered Maxey and the seventh-seeded Philadelphia 76ers on Sunday, winning 123-91 at TD Garden to take a 1-0 series lead.

Maxey lamented that the game didn’t even feel like playoff basketball for Boston, which led by double digits for the final 37 minutes.

“I think this is my fifth playoffs, so losses, whether you lose by seven, 12, 100, they all hurt. They all don’t feel good,” Maxey told reporters. “But this one, it sucks. We didn’t expect this at all. But we’ve just got to play better. You know, Paul (George) said something that kind of registered in my mind: They didn’t feel like it was a playoff game. We did, but they didn’t. You know what I’m saying?

“They just did us easy. I feel like it was an easy game, and that’s not OK. We’ve got to make them more uncomfortable.”

George, the Sixers’ nine-time All-Star wing, said Philadelphia didn’t offer nearly enough resistance, especially on Celtics drives. Boston went 17-for-19 on shots at the rim, with Jayson Tatum and Jaylen Brown making nine of their 11 attempts inside the restricted area.

“I don’t think we matched the physicality, the toughness,” George told reporters. “Essentially, they had a lot of possessions where they just walked to the rim for easy layups. There was just no resistance at a lot of times throughout the game, and that’s not playoff basketball.”

Maxey agreed.

“I think most of the immediate stuff is, like, if you see somebody driving to the rim, step in front of them, no matter what their scenario, especially if it’s Jaylen or Jayson,” he said. “Step in front of them, make them kick the ball out, then rotate off of that. But they got like, wide-open, walk-down-the-lane layups, walk-down-the-lane dunks, I think Payton Pritchard got one, too. Those are the ones we can’t give up. It’s going to be tough regardless, and we’re capable of doing it, but we can’t give those types of plays up.”

The Celtics also bottled up Maxey, the NBA’s fifth-leading scorer during the regular season. The All-Star guard scored 21 points but shot 8-for-20 from the field and generated just five free-throw attempts. George added 17 points on 4-of-8 shooting. The 76ers were playing without their third veteran star, center Joel Embiid, who has been out since undergoing an emergency appendectomy earlier this month.

Brown called the win a great example of “Celtics basketball.”

“We’ve been a hard-playing team all year,” he said. “That can’t just change now that the playoffs have started. But then it’s just focusing in, honing in on the details and just winning the fight. Being the harder-playing team and just guarding. Our offense can win us this series. I mean, our offense is important, but we’ve got to make sure we guard. I thought (on Sunday) we did a great job.”