Porzingis makes triumphant return, Shai strikes for 48 in win
Jason Tatum contributed 20 points, eight rebounds and eight assists for the Celtics while Pritchard had 22 points off the bench for the reigning NBA champions and set a record for most three-pointers in a season by a reserve player.
In other games, NBA scoring leader Shai Gilgeous-Alexander struck for a game-high 48 points to lead Oklahoma City in a 113-107 victory at Detroit.
In Brooklyn, Latvian center Porzingis was not at full strength at the start but found his form as the game continued.
"At first I felt a little out of rhythm," Porzingis said. "First few shots were a bit bricky, but as the game went on I felt better and better. Happy to be back.
"I'm not feeling in shape yet. It has been tough these past couple weeks, but in these kind of moments you've got to bite down and bring something from deep. That's what I tried to do and I'm just happy we got the win."
Pritchard sank his 219th three-pointer of the season in the fourth quarter, giving him the NBA season record for three-pointers by a bench player.
In all, he made 7-of-11 shots, 5-of-8 from three-point range, and sank three free throws in the final 8.2 seconds to secure the Celtics' 13th victory in 16 games.
Boston improved to 49-19, second in the Eastern Conference, eight games behind NBA overall leader Cleveland.
At Detroit, Gilgeous-Alexander made 17-of-26 shots from the floor, 4-of-6 from three-point range, and all 10 of his free throws.
The Canadian guard also had six assists, four rebounds and three steals to spark the Western Conference-leading Thunder, which improved to 55-12 and 18-3 since the start of February.
At Memphis, Jaren Jackson Jr. scored 31 points while Desmond Bane added 22 points, 10 rebounds and eight assists to spark the host Grizzlies over Miami 125-91.
The Houston Rockets stretched their win streak to six games and matched Memphis at 43-25 with a 117-114 home victory over Chicago.
Jalen Green led Houston with 28 points while Turkish center Alperen Sengun had 24 points and 15 rebounds for the Rockets.
Denver fell into a three-way tie for second in the West with Memphis and Houston with a shock 126-123 home loss to woeful Washington (15-51).
Serbian center Nikola Jokic led Denver with 40 points, 13 rebounds and nine assists but Alex Sarr led the Wizards with 34 points and Jordan Poole sank the deciding three-pointer for Washington with 2.1 seconds remaining.
Greek star Giannis Antetokounmpo scored 34 points to lead Milwaukee over visiting Indiana 126-119 while Devin Vassell led seven San Antonio scorers in double figures as the Spurs beat visiting New Orleans 119-115.
Warriors beat Knicks
Steve Kerr, who has guided Golden State to four NBA crowns, became the winningest coach in Warriors history, passing the 557 wins by the late Al Attles for the most regular-season triumphs in team history, when the Warriors beat visiting New York 97-94.
"It's incredible. I'm thankful that I have been here for every single one of his wins," Warriors forward Draymond Green said. "He's a special guy. He has made this a special place. We're lucky to have such a winner as that."
Stephen Curry scored 28 points, including three clinching free throws in the final 14.1 seconds, to lead the Warriors to their seventh consecutive victory and 14th win in 16 games.
"It feels great to walk in and know you have a chance to win. That's what we play for," Green said. "We put a lot of work in to play on the biggest stage. To put these wins together, it feels amazing."
The Warriors are 14-1 when Jimmy Butler plays. The former Miami star was traded to Golden State last month.
"It's a real ball club now. With him on this team, whether he has 11 points or 30, he makes us a real ball club," Green said.
"And when we're a real ball club, we usually win championships."