"In the fourth quarter, they did a good job of making shots," O'Neal said. "Ray, Paul and the others have an incredible comfort level with each other. We've got to figure a way to keep those guys down, especially when we're up 15 or 16 points in a game."
With the score tied 84-all, Boston center Kendrick Perkins, who had trouble containing O'Neal most the game, blocked a turnaround and Pierce hit a jumper on the other end, giving the Celtics an 86-84 lead with 1:38 left.
On the ensuing possession, O'Neal lost the ball out of bounds. Pierce then hit a 17-footer to give Boston a four-point edge before putting the game away with a spinning, driving scoop shot that made it 90-84 with 34.4 seconds left.
When the ball went through the hoop, Pierce turned and pump his right fist as the Raptors called timeout.
Boston, which trailed by 15 points early in the third quarter and by six entering the fourth, used a scrappy, trapping halfcourt defense to bottle up the Raptors' offense while going on a 9-2 run to close the score to 71-70 on Pierce's jumper with 8:19 to play.
The teams traded 3-pointers -- with Pierce getting both for Boston -- before Eddie House made a 3 from the right corner to give the Celtics their first lead since the game's opening minutes, 79-77, with 4:45 to go.
Toronto had opened a 57-42 edge on Jose Calderon's jumper 3½ minutes into the third quarter before Boston started its comeback. Garnett scored six points and Pierce five during a 15-4 run as the Celtics closed the gap to three before Jason Kapono hit a 3-pointer to give the Raptors a 65-59 lead after three.
O'Neal, ineffective in a season-low 19½ minutes of action with only five free throws in Sunday's 89-79 win against the Charlotte Bobcats, took control inside early in the game. He scored 10 of the Raptors' first 14 points as they opened a 23-18 edge after one.
Toronto, which outplayed Boston in the paint and held the Celtics to 32 percent shooting, led 48-36 at halftime. O'Neal had 19 points on 7-of-12 shooting in opening half.
The Raptors pushed their advantage to 16 points twice in the second quarter, the second when O'Neal eclipsed his previous season-high with two free throws to make it 46-30 late in the half.
Chris Bosh, who scored 30 and grabbed 15 boards in the win at Charlotte, had only nine points. ... Pierce went just 2-for-10 from the floor in the first half. ... The Raptors gave Boston just one of its six home losses last season, hitting 15 3-pointers in a 114-112 win on Jan. 23. ... Boston G Rajon Rondo had his left elbow wrapped in ice the locker room before the game. ... Toronto had more assists (13) than Boston had baskets (12) in the first half.