The Celtics saw their five-game winning streak come to an ugly end on Sunday as the Knicks blew out their rivals at TD Garden.

Boston was shorthanded for the matchup, missing starting forward Sam Hauser due to back spasms and that forced the hosts into some new-look lineups. Boston started with double bigs for the third straight game and also played two-way forward Ron Harper Jr. for big minutes off the bench.

Nikola Vucevic came off the bench for Boston in his second game since his acquisition from the Bulls last week. The big man finished with 11 points in 23 minutes but struggled with his shot 5-of-13 like much of his teammates. The Celtics shot 37 percent from the field and the second unit particularly struggled, with the group collectively going 1-of-18 from 3-point range.

The moving parts is creating a bit of a challenge for Boston on the floor but Jaylen Brown (26 points) pointed out one thing he wanted to see from the Celtics’ new addition after the loss.

“We got to figure out the chemistry a little bit, the flow a little bit,” Brown said. “We want Vuc to be a little bit more aggressive, looking for him to get going and make him feel confident in taking those shots and where he can catch the ball. I think he’s still learning, but we need him to be aggressive. So we’ll make adjustments, we’ll communicate, we’ll watch film, and we’ll be better for it.”

Vucevic averaged 13.8 shots per game this season in Chicago but has only averaged 10.5 attempts per game in his first two appearances in Boston. He faced a stiff challenge against a Knicks front line on Sunday that kept the Celtics out of rhythm for much of the night.

“There’s a high level of physicality and execution that’s required when you play against great teams,” Joe Mazzulla said. “So we’ve played great basketball for a long time in this small stretch and have taken the game to that level of physicality and execution. Tonight wasn’t our best. Tonight, they took it to that level of physicality and execution, and so I think that’s what you take from it, right? There’s a level that you can get to, and you’ve got to work to stay there as long as you can. We did it for really good stretches of time here recently and tonight, we didn’t.”

The Celtics will have a chance to work on integrating Vucevic more into the team’s system in the next two weeks with a practice scheduled on Tuesday and an All-Star Break that will allow for some practice time upon the team’s return next Thursday. For now, Brown isn’t going to let one loss get him down as the team works to adjust to its new roster pieces.

“I feel like we competed,” Brown said. “I feel like we did the stuff, the intangibles that we needed to do. We didn’t turn the ball over a lot. We rebounded well. Those are the two things that, in the past, have been our Achilles’ heel. We did pretty good on those things. It came down to the offensive end, where we just had to make some shots. Scoring 89 points not gonna get it done. We gotta figure out how to put that ball in the cup.”