The Hawks will not soon forget this one.

They wasted one of the greatest individual playoff performances in franchise history – a 45-point, 13-rebound, four-block effort from Paul Millsap – in a 104-95 overtime loss to the Celtics in Game 4 of their playoff series Sunday night at TD Garden.

The best-of-seven Eastern Conference first-round series is tied at 2. Game 5 will be Tuesday night in Atlanta.

The Celtics outscored the Hawks 12-3 as Amir Johnson scored the first five points of overtime. Isaiah Thomas put a dagger through the Hawks with a corner 3-pointer with 30 seconds remaining for a 102-95 advantage.

The Hawks are 0-6 in overtime this season after failing in five regular-season chances.

“I felt like they had a little momentum there once they got those quick baskets,” Al Horford said. “A couple of mistakes on the defensive end, especially the second one in transition. Those are the ones we can’t give up. We gave it up at a critical time in the game.”

The Hawks trailed 90-86 with 1:22 remaining after Jonas Jerebko hit a 3-pointer. Jeff Teague then hit two consecutive 3-pointers – in a span of 29.7 seconds – to give the Hawks a two-point lead with 20.2 seconds left. Thomas drove the lane for an easy layup to tie the game at 92 with 15.0 seconds left.

The Hawks held for a final attempt as Teague dribbled and the shot clock went under three seconds. He could not get a shot off, with Thomas defending, and the game went into overtime.

“The ball slipped out of my hand,” Teague said.

On the final play, Kyle Korver was to slip off a fake screen. The Celtics didn’t bite.

“You want to exhaust the clock in that situation,” Hawks coach Mike Budenholzer said. “You want to get the last shot. I think Jeff just ended up mishandling it a little bit. That was just Jeff against Isaiah Thomas to obviously get a good look, a good opportunity, and not leave any time on the clock.”

Millsap had the most points by a Hawks player in a postseason game since Dominique Wilkins scored 47 against the Celtics on May 22, 1988.

“Did we win?” Millsap asked of his stellar game.

Millsap finished 19 for 31 from the field to finish one point shy of his career-high of 46 points. The rest of the Hawks starters were 11 of 47. Millsap accounted for 47 percent of the Hawks offense. Teague was the next highest scorer with 13 points.

“He was our offense,” Horford said.

Millsap finished with 26 points on 11-of-16 shooting, including 3 of 4 from 3-point range in just the first half. The Hawks all-star power forward had 26 points combined in the first three games of the series.

Thomas led the Celtics with 28 points. Marcus Smart added 20 points including two big 3-pointers in the fourth quarter.

The Hawks took a 48-46 lead into halftime after closing the second quarter on a 13-5 run, including a 10-0 streak. Millsap had 10 of the points, including two 3-pointers.

Millsap’s struggles in Games 1-3 were frustrating for the Hawks’ leading scorer. He was 10 of 32 from the field. He said it was his responsibility to be more aggressive getting to the basket and making the open shots he did have.

“I just put an emphasis on being aggressive. I felt I wasn’t aggressive the first three games. Especially on the road, with your back to the wall, you have to be aggressive. I just wanted to do that tonight and set the tone.”

The Hawks opened the third quarter on a 14-0 run to take a 16-point lead, 62-46. Millsap had seven of the points. He eclipsed his previous playoff-high total of 29 points in the run.

It wasn’t over.

The Celtics chipped away at the Hawks’ big lead and cut their deficit to three points, 73-70, at the end of three quarters. The Celtics scored the last eight points of the quarter, including two 3-pointers from Jerebko.

The Hawks’ winless record in overtime is a point of concern.

“I can’t put my finger on it,” Millsap said. “I think it’s something as a group we have to figure out. Because we have lost a lot of games in overtime. We have the guys to do it. I think we are smart enough to figure it out.”