Kristaps Porzingis had 34 points and a career-high-tying eight 3-pointers, including one in the third quarter with a foot on the Knicks’ logo, as visiting Boston downed New York 119-117 in overtime Tuesday night.

With their ninth straight win on the road, the Celtics secured their first four-game regular-season sweep of the Knicks since the 2019-2020 season.

By virtue of the Cleveland Cavaliers’ win over the Chicago Bulls, Boston (59-20) is locked in as the No. 2 seed in the Eastern Conference. New York (50-29) needs one more win or an Indiana Pacers loss to lock up the No. 3 seed.

Porzingis, the former Knick, had the biggest shot of the night, making a three with 40.8 seconds left in overtime to break a 112-112 tie. The Knicks turned the ball over on their next possession and Jrue Holiday made four free throws in the final 12.6 seconds to clinch it for Boston.

Jayson Tatum had 32 points for the Celtics. Jaylen Brown played only 22 minutes while dealing with a sore right knee and scored six points. Jrue Holliday scored 16 points and Derrick White chipped in 14.

For the Knicks, Karl-Anthony Towns had 34, Jalen Brunson added 27 and Josh Hart finished with 10 points, 11 rebounds and seven assists before fouling out.

New York led by three with under a minute left in regulation after a basket by Mikal Bridges (14 points), but Towns fouled Tatum on a 3-point shot. Tatum made the first two free throws but missed the third.

Hart scored on a layup to make it 107-104 with 11 seconds left, but Tatum answered with a three with 2.9 seconds to play. The Celtics shot 19-of-49 from 3-point range overall.

Hart missed a long three at the fourth-quarter buzzer that could have won it for the Knicks.

New York controlled the first half behind Towns, who had 22 on 9-for-13 shooting at the break.

Towns scored 10 straight points for the Knicks as they built a 14-7 lead.

Boston pulled to within three on a long 3-pointer by Sam Hauser and a traditional three-point play by Tatum. After the first quarter, New York led 30-27.

The second quarter followed a similar script. Towns made a nifty hook shot in the lane and then banked in a jumper from the elbow with eight minutes left to put New York ahead 42-33, its biggest lead to that point.

The Knicks’ lead hit 11 at 52-41 after a pair of Anunoby free throws with 3:58 left, but Boston surged back. Porzingis drilled a three, sank a free throw and scored from inside to key an 11-2 run.

New York led 58-52 at half.