Jalen Brunson had 39 points and 12 assists, and the New York Knicks moved a win away from their first Eastern Conference finals appearance in 25 years and pushed the defending champion Boston Celtics to the brink of elimination with a 121-113 victory Monday night in Game 4 at Madison Suare Garden.

The Celtics will have to make the NBA’s 14th comeback from a 3-1 deficit to extend their title reign and may have to do it without All-Star Jayson Tatum, who was carried off the court with a right leg injury with 2:58 left.

Mikal Bridges and Karl-Anthony Towns each added 23 points and OG Anunoby bounced back from two poor performances by scoring 20 for the Knicks, who can win the series Wednesday night at Boston. If not, they would come back to Madison Square Garden to try to do it Friday night.

Tatum scored 42 points, his high in these playoffs, before he was hurt when the Celtics turned the ball over and his leg gave out as he tried to lunge forward toward the loose ball.

The Knicks had taken control just before that in front of a delirious crowd of fans who haven’t seen them play in the conference finals since they lost to Indiana in 2000.

Nobody has come from 3-1 down since Denver did it twice in 2020 at the Walt Disney World resort. It hasn’t happened when a team had to win a true road game since Cleveland rallied past Golden State in the 2016 NBA Finals.

After leading by at least 20 points in the first three games — but blowing the first two of them in Boston — the Celtics had another double-digit lead less than five minutes into this game.

They led 62-51 at halftime, but the Knicks played their starters the entire way in a desperate third quarter in which they outscored the Celtics 37-23 to set up a thrilling final period.

Tatum’s three-point play tied it for the final time at 102-all before Anunoby hit a 3-pointer and the Knicks later put it away for good with an 11-0 burst that made it 116-104.

Derrick White made six 3-pointers and scored 23 points for the Celtics. Jaylen Brown had 20.

Cavs’ Mitchell questionable for Game 5: Cavaliers star Donovan Mitchell is listed as questionable for Cleveland’s pivotal Game 5 of its second-round series against the Indiana Pacers after reaggravating a sprained left ankle on Sunday.

The All-Star guard had an MRI on Monday, which confirmed the sprained ankle. He did not play the second half of the Cavaliers 129-109 loss at Indiana after he appeared to experience pain while warming up during halftime.

His status for tonight’s game is likely to go down to game time.

Mitchell first suffered the injury on April 6 during the second half against the Sacramento Kings. He stepped on the foot of Sacramento’s Keon Ellis near midcourt before losing his balance and rolling his left ankle.

Mitchell missed the last four games of the regular season due to the injury. He finished with 12 points in 20 minutes as the top-seeded Cavs trailed 80-39 at halftime.

The No. 4-seeded Pacers, up in the series 3-1, can close it out Tuesday in Cleveland, where they’ve already won twice.

Mitchell is averaging 28.9 points during the playoffs, including five games with at least 30 points.

Thunder take on Nuggets: Oklahoma City might have saved its season with a 92-87 win at Denver on Sunday that tied the Western Conference series at two wins apiece. The Thunder finally won a close game in the series on Sunday after losing Game 1 on a last-second shot and Game 3 in overtime.

“I think we fought, stayed the course, played the game,” Thunder guard Shai Gilgeous-Alexander said. “Especially in this series, it’s been so random almost. It’s throwing different things at us. I think we’ve been able to stay the course and it gave us a chance late. We closed it out.”

The Thunder regained the homecourt advantage they worked so hard to get in a franchise-best 68-14 regular season. But lose tonight, and they head to Denver down 3-2 and facing elimination.

“I mean there’s no relief at all,” Thunder forward Chet Holmgren said after Sunday’s win.