Pierce lobbied to stay in the game, then made the tiebreaking jumper with eight seconds left as the Boston Celtics beat the New York Knicks 104-101 on Wednesday night.
Playing on his 33rd birthday, Pierce knocked down his jumper from just inside the 3-point arc to ensure there would be no overtime that would wreck his party plans.
"I got an 11 o'clock reservation I had to make," Pierce said. "I didn't want to stay any longer than I had to, you know what I'm saying? It's my birthday."
The Celtics overcame a big first home game at Madison Square Garden for Amare Stoudemire, who scored 30 points in three quarters. But he was on the bench along with the rest of the Knicks starters down the stretch, when the Celtics pulled it out.
"I didn't plan on extending them and then they wanted to stay in there, they were having fun. Paul said he wanted to win, it was his birthday," said Rivers, who along with Jermaine O'Neal also celebrated a birthday.
Down eight midway through the fourth, the Celtics rallied to tie it at 101 on two free throws by former Knicks guard Nate Robinson with 1:09 left. The teams turned it over on the next three possessions before Pierce's jumper.
Rookie Andy Rautins had a 3-pointer partially blocked after mishandling the inbounds pass on New York's next possession, and Pierce closed it out with a free throw.
Ray Allen scored 24 points and Pierce had 20 for the Celtics, who brought back their starters after they sat out a loss in Philadelphia on Tuesday. Shaquille O'Neal was held out while resting his right hip.
Wilson Chandler had 13 for the Knicks, who had played just a pair of games in Europe and were starting a stretch of six games in 10 days to close the preseason.
Stoudemire powered his way to 16 in the third quarter, when the Celtics had nobody to guard him after Kevin Garnett was ejected in the first half.
"We got out and ran," Stoudemire said. "We definitely didn't wait for those guys to set their defense. We took the ball out. We ran with it with a purpose. We played agressive. They had a hard time stopping us."
But with Allen, Pierce and Rajon Rondo on the floor at the end, Boston was too good for New York's reserves.
"I'm sure a veteran team like that don't go real hard in practice, so they have to have minutes to be in game shape. I'm sure that's why he did it," Knicks coach Mike D'Antoni said.
Boston scored the first seven points, then New York answered with seven in a row en route to a 26-25 lead.
Things bogged down in the second as the referees, instructed to call more technicals this season for overt gestures and too much complaining, whistled four in 16 seconds. Two went to Garnett, who could only laugh as he was thrown out with 4:39 remaining.
The Knicks led 56-51 at the break, then were up by 10 early in the third quarter before settling for an 82-77 on Raymond Felton's 3-pointer at the buzzer.
The teams meet again Saturday in Hartford, Conn. ... O'Neal said there was some early interest from the Knicks during free agency. "I felt Boston was a better fit for me, playing alongside in my opinion three to four first-ballot Hall of Famers," O'Neal said. "So it's going to be a fun year for me."