NEW YORK — Jalen Brunson and the New York Knicks had just taken control of the game with another fourth-quarter kick when Jayson Tatum fell to the court with a potentially severe right leg injury.

The specifics of Tatum's injury are uncertain, but the situation in the Eastern Conference semifinals is clear.

The Knicks need one more victory to reach the conference finals for the first time in 25 years. The Celtics need to match the biggest comeback in NBA history to extend their title reign.

Brunson had 39 points and 12 assists, and the Knicks pushed the defending champion Boston to the brink of elimination with a 121-113 victory Monday night in Game 4.

Blown out in Game 3, the Knicks dominated the second half to become the first home team to win in this series.

"I think it was a sense of urgency, desperation, just knowing that we have a great opportunity," Brunson said.

The Celtics will have to make the NBA's 14th comeback from a 3-1 deficit, and may have to do it without Tatum, who was carried off the court with a right leg injury with just shy of three minutes left to play.

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, which can win the series Wednesday night in Boston. If not, they will come back to Madison Square Garden to try to do it Friday night.

"We have to turn that page quickly and do our first job, which is to win on Wednesday. That's the mindset," Celtics veteran Al Horford said. "As a group, we just have to rally together, because, obviously, we've lost our leader, the guy that gets us going."

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.

"They hit us early, and, obviously, we got into a hole," Knicks coach Tom Thibodeau said.

"I love the way we fought back. We showed a lot of toughness and more discipline in the second half, and made timely plays. Everybody worked together on both ends of the floor."

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, and were up 62-51 at halftime.

Brunson then scored 18 in a desperate third quarter, when the Knicks played their starters the entire way and outscored the Celtics 37-23, setting up a thrilling final period.

"Just keep fighting," Bridges said. "We were down way worse before."

Tatum's three-point play tied it for the final time at 102-all, before Anunoby hit a 3-pointer and the Knicks 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.

"I got back there, talked to the medical staff and they told me it's a lower-body injury for Jayson Tatum and we'll get an MRI in the morning," Celtics coach Joe Mazzulla said.

A jumper in the lane by Bridges made it 111-104, and Anunoby added a steal and dunk to increase the gap to 113-104 with 3:03 left.

Tatum was injured on the latter play and grabbed his ankle and signaled for a timeout with 2:58 to go.

"It's very concerning from the care we have for him, what he means to us and what he means for Boston," Horford said.

"It's very tough for us. More importantly, this is very tough for him right now. It's very tough for our group altogether."

Tatum was helped off the floor with his right foot elevated and was later seen being pushed to the locker room while sitting in a rolling chair.

Brunson nailed a three-pointer to cap the run and all but seal it at 116-104 with 2:25 remaining.

Agencies