BOSTON -- Like he has done so often this season, forward Jae Crowder did it at both ends of the floor for the Boston Celtics on Sunday night.

"Jae's playing at a high level right now on both ends," coach Brad Stevens said after Crowder scored 18 points and hounded New York's Carmelo Anthony as the Celtics won their fourth straight game and handed the New York Knicks their fourth straight loss with a 100-91 decision.

Crowder scored 13 points in the third quarter and spent most of his night chasing Anthony, who scored a game-high 29 points and grabbed 10 rebounds but was just 111 of 26 from the floor.

"We need him to defend the way he is," said Stevens. "The thing about Jae (is) that I think Jae has really improved on throughout the years; being in the right place at the right time from a position standpoint because he's so … he's a good physical defender when he's there."

Asked about the defense, Anthony said, "I think everybody, not just Jae. I think everybody (did) a great job, especially with me in particular.

"They like to get up in my space, they like to force me into the bigs. So you've got to think a lot, you've got to figure out a lot out there on the court."

Crowder, who also had six rebounds, said, "watch film" is a key to his improving defense, adding, "I still have the heart and passion on the defensive end and I just watch more film on my opponent and try to study as much as possible."

The Celtics, who won in Detroit on Saturday night, improved to 18-13 and moved within a game of the idle Toronto Raptors in the Atlantic Division. Boston's next three games are at home against the Los Angeles Lakers (Kobe Bryant's last visit) and a home-and-home with the Brooklyn Nets -- two teams with a total of 13 wins between them.

The Knicks, who hit just four of 19 attempts from 3-point range, fell to 14-18.

"They have several guys that are good on-the-ball defenders," said Knicks coach Derek Fisher. "Very active team."

Boston guard Isaiah Thomas scored eight points late and finished with 21 points, eight rebounds and six assists. Guard Evan Turner came off the bench to contribute 19 points and five rebounds, and reserve forward Kelly Olynyk had 11 points and nine rebounds.

New York rookie forward Kristaps Porzingis had 16 points and 12 rebounds but sank just four of 13 shots from the floor. Playing with an injured finger, he was 8 of 8 from the foul line, but couldn't connect from the floor down the stretch. "Not only down the stretch, just the whole game for me and some of my teammates," he said.

The Celtics led by 14 with 10 minutes left and then had to hold off a charge that got the Knicks as close as five with 4:48 remaining. However, as New York went ice cold, Thomas hit two consecutive baskets, and the lead was back to nine with 2:40 remaining.

Boston guard Marcus Smart returned after missing 18 games with a leg injury and played just over 13 minutes, producing a three-point play a minute after entering the game in the second quarter. He hit a 3-point shot in the second half and finished with six points and three rebounds. He would have gone back in at the end if the Celtics needed a key defensive stop.

The Knicks, outscored 57-35 in the second half in losing at Atlanta on Saturday night, turned the ball over six times in the first 4:16 of the second half Sunday as the Celtics grabbed control of the game.

The Knicks shot just 37.1 percent from the floor, the 10th Celtics opponents -- and third in a row -- to shoot under 40 percent, tying Boston for the league lead.

Said Anthony: "I think when you're kind of fighting an uphill battle the whole game, even when you cut the lead to five with a couple of minutes to go in the game, you're hoping and praying that everything goes your way."

NOTES: Boston F David Lee missed his second consecutive game with back spasms. ... Knicks coach Derek Fisher, reacting to F Carmelo Anthony saying after Saturday night's loss at Atlanta that the players have to want winning more, said before the game, "For sure. The players are the ones that have to make the plays. We can create game plans, strategies, coverages, etcetera, but when the game starts it's really those guys that have to get it done. Anything you want to accomplish has to start and end with them, and I think we're making good progress, but when you play against really good teams, you have to embrace that."