An energized Isaiah Thomas scored 33 points, as the Celtics beat the Bulls 104-95 to tie the series 2-2.
After two sub-par performances in Boston, the Celtics have regained home-court advantage in this best-of-seven series, which now heads back to TD Garden. Neither team has won a home game in this series.
The play that sealed the victory for the Celtics wasn't a twisting Thomas drive, but rather the 5'9 guard taking a charge on Bulls power forward Bobby Portis with 2:15 remaining in the game. The score was 99-88 and that play sent many Bulls fans to the exits.
Thomas paced the Celtics with 16 first half points, including several of his vintage drives through the heart of the Bulls' interior defense.
Gerald Green exploded for 16 first half points and 4-7 three-pointers, as the Celtics cruised to 57-46 halftime lead.
Green started his second game in a row since coach Brad Stevens shuffled his lineup. Green hadn't started a game with the Celtics since his first tour with the team in 2007.
Bulls guard Jimmy Butler led the Bulls with 17 points in the first half and finished with 33 points. Celtics defensive stopper Avery Bradley shut down the Bulls all-star in game three, holding Butler to 7-21 shooting from the field with no foul shots and no assists.
The Celtics sputtered out of the halftime break as the Bulls' Robin Lopez dominated the paint and Butler continued to assert himself. The Bulls took the lead 65-63 with 5:12 remaining in the third quarter. Thomas received his fourth foul at 7:58.
The third quarter was marked by big swings. The Bulls went on a 19-6 run and the Celtics responded with a 16-5 run. The third quarter ended with the Celtics on top 79-70.
In the initial three games the Bulls outrebounded the Celtics by an average of 49-37 and the Celtics closed the deficit in game four to 44-41.
The Celtics got off to a 14-4 start midway through the first quarter behind a pair of 3-point shots from Green and one from Thomas.
The Celtics lead ballooned to 41-21 with 9:47 remaining in the second quarter behind a couple of 3-point shots and layup from Green.
The Celtics have had an emotional week while coping with the loss of Thomas' 22-year-old sister Chyna, who was killed in a car crash on April 15.
Stevens said Thomas was very engaged during Sunday's pregame shoot around, but said only Thomas could describe how he's handling his sadness and mourning.
After the game Thomas said, "mentally and emotionally I'm not here."
Prior to game four, former Celtics star Kevin Garnett met with the team and offered a rousing speech about purpose in the playoffs.
The series resumes April 26 for game five at the TD Garden. The start time has yet to be determined.