The Knicks will look to bounce back quickly from the beating they took in Boston on Tuesday to open the season, and they must start on defense.

The Celtics raised the banner to commemorate their 2024 NBA title and then thumped the new-look Knicks, who are looking to challenge the Eastern Conference champions this season.

“This is championship-level basketball. It was a slap in the face for us and we have to react,” guard Miles McBride said after the game. “Of course it’s a long year. I can’t overreact to a game, but I don’t think you go into a year like that and set the tone.”

It's hard to disagree with that assessment after the Knicks flopped in their first game with new starters Mikal Bridge and Karl-Anthony Towns, acquired in separate offseason trades.

“I have a lot of confidence in our offense. “We have to have the defensive identity that makes us special,” Towns said. “Once we figure that out, we'll take the next step and be able to be the team we want to be.”

Bridges had no answers for his primary defensive task, All-Star forward Jayson Tatum, who led the way with 37 points and scored eight of the Celtics' NBA-record 29 points on 3-pointers.

They shot an outstanding 60.4 percent from distance (29 for 48) at one point before missing their final 13 attempts from distance as they attempted to set a new mark.

“Indecision. Second and third tries,” Tom Thibodeau said when asked what went wrong defensively. “When you play against a team like that, you have to fight and fly around.

“One effort will not be enough. You have to make a second, third and fourth attempt.”

The Knicks will focus on improving their defensive performance in their home opener Friday night at the Garden against the Pacers, the team that eliminated them in the second round of the playoffs last spring.

All-Star guard Jalen Brunson said having two new starters was “the easy way out” because “we still got our asses kicked.”

“They've been here a long time and we're a pretty new team, but that's no excuse,” added Brunson, who scored 22 points but was minus-23 in 24:30 of playing time. “Personally, I have to get better. It starts with my approach and everything, and I just have to get better.

“We can say a lot. We can dismantle anything. They made a lot of 3s. They probably earned more than we took. But we have to be better on both sides. I have to be better on both sides.”

The same goes for OG Anunoby, who was minus-21 on 1-for-7 shooting with just four points. And for Bridges and Towns, both of whom suffered ineffective two-way debuts.

Obviously, it will take some time for the altered starting lineup and rotation to come together following the departures of Julius Randle, Donte DiVincenzo and free agent Isaiah Hartenstein, as well as the absence of injured center Mitchell Robinson.

“We look at what we did, what we needed to fix, and then we get back to work,” Thibodeau said. “Every game reveals things to you. Sometimes you do things well, sometimes not as well as you need to. But understand why you lost or won and take the necessary steps to move forward.”