NEW YORK — For a game that essentially meant nothing to the Celtics, they refused to relent anything to the rival Knicks as they prepare for a potential collision in the Eastern Conference semifinals.

Former Knick Kristaps Porzingis, who unceremoniously left the club nearly six years ago, was brilliant in his rare return to Madison Square Garden. He completed a 34-point masterpiece with a stepback 3-pointer as he was being knocked to the floor and the Celtics edged the Knicks, 119-117, in overtime.

Porzingis nailed eight 3-pointers and was the best player on the floor in stretches for the Celtics, who swept the season series. Jayson Tatum sent the game into overtime with a stepback 3-pointer with 2.9 seconds left.

With a win at Orlando on Wednesday, the Celtics can tie the 2016 Golden State Warriors for the best season road record in league history. Jrue Holiday added 16 points and Derrick White scored 14. Karl-Anthony Towns led New York with 34 points, just 12 after halftime, while Brunson scored 27.

New York allowed the Celtics to hang around in the first half and paid for it in the second. Boston began the third period on an 8-0 run in the first 92 seconds, including back-to-back 3-pointers from Jrue Holiday and Porzingis.

Porzingis hasn’t made many returns to New York since being traded to Dallas in 2019, but he made the most of his time in the spotlight, wowing the MSG crown with three more 3-pointers as the Celtics took the lead in the third period.

A Jaylen Brown layup gave the Celtics a 76-71 lead before the Knicks stormed back on a 7-0 run, partly because of Boston turnovers. Holiday, who has returned to form after his finger injury a month ago, brought Boston back with a layup and 3-pointer while Tatum ended the period with a contested stepback jumper from the corner for a 83-78 lead.

Brown, obviously laboring at times with that balky right knee, struggled with 6 points on 2-for-8 shooting in 22 minutes. He came out with 2:46 left in the third quarter and watched the rest of the way.

The Celtics held Towns in check during the first three meetings, limiting him to 45 points. He scored 22 in the first half Tuesday, as he capitalized on every switch the Celtics offered, scoring a bucket on all five of his defenders.

He was 9-for-13 from the field along with nine rebounds while Brunson, in his second game back from missing 15 games with a sprained ankle, added 12 points as the Knicks led 58-52.

With little to gain besides a shot at the all-time road record, the Celtics spent the first half keeping within striking distance. An 8-0 run late in the first half drew Boston to within 2 as Tatum and Porzingis combined for 29 points on 10-for-23 shooting and five 3-pointers.

The remaining Celtics struggled offensively, especially Brown, who was assigned at times to check Towns and got into foul trouble. He scored 2 points in 13 first-half minutes on 1-for-5 shooting and two of the Celtics’ four turnovers.

There was no issue creating open 3-point looks, but the Celtics had trouble knocking those down. They were 8 for 26 from the 3-point line.

Porzingis made his second appearance against the Knicks this season and looked comfortable punishing mismatches and converting the open 3-pointer. He sat out two of the past three games for rest.

While the Knicks are essentially locked into the third seed, this appeared to be an important game for their psyche. They entered 1-8 against the top four teams in each conference, including 0-3 against the Celtics. Boston won those meetings by an average of 21 points, including a 27-point victory on Feb. 8 at MSG.

The Celtics listed four starters as questionable and White as probable but all five were available.

Gary Washburn is a Globe columnist. He can be reached at [email protected]. Follow him @GwashburnGlobe.