Pierce muscled in for the go-ahead layup with 25 seconds left, and the surging Celtics avoided a late collapse to beat the struggling Heat 92-91, for their eighth consecutive victory.
"I'd been struggling with a strain in my back all night," said Pierce, who finished with just 12 points. "But coach (Doc Rivers) saw tremendous confidence in me and I wanted to be there for my teammates in the end."
Pierce's basket put the Celtics back on top after squandering a 15-point fourth quarter cushion. However, the game was left in the hands of Miami's All-Star guard Dwyane Wade, who made his season-debut 48 hours earlier, following off-season shoulder and knee surgeries.
After a timeout, Wade received the inbounds at the top of the key and dribbled down the clock. With a chance to pull out the improbable victory, he launched the potential-game winning jumper over former teammate James Posey. But it banged off the back of the rim and Posey ran down the miss as time expired.
"There was a lot of stuff going through my head: Being out six months and my second game back," said Wade, who led Miami with 23 points. "I had an opportunity to win the game against the best team in the league, record-wise, in the Boston Garden."
Kevin Garnett had 26 points and 11 rebounds while Ray Allen added 19 points for the Celtics, whose 8-0 start is the best since the 1972-73 club ran off 10 in a row.
Ricky Davis had 20 points for the Heat (1-8) while Shaquille O'Neal finished with 17 and nine boards.
Elsewhere Cleveland Cavaliers 99, Utah Jazz 94 LeBron James poured in 40 points, including four game-sealing free throws with 3.8 seconds left, to go along with 10 rebounds, nine assists and a key block as the Cavaliers snapped the Jazz's five-game winning streak.
Utah's Carlos Boozer had 26 points and 11 rebounds.
Seattle SuperSonics 126, Atlanta Hawks 123 (double overtime) Rookie phenom Kevin Durant hit the game winning buzzer-beating three-pointer, and Damien Wilkins had a career-high 41 points, lifting the visiting Sonics past the Hawks.
Joe Johnson paced the Hawks with a season-high 39 points.
San Antonio Spurs 90, Houston Rockets 84 Tim Duncan had 25 points and 13 rebounds as the Spurs took advantage of the absence of injured Tracy McGrady to hand the Rockets their third straight setback.
Argentine rookie forward Luis Scola led Houston with a career-high 20 points on 10-of-11 shooting.
Orlando Magic 95, New Jersey Nets 70 Rashard Lewis scored 27 points while Dwight Howard had 21 and 19 rebounds, helping the Magic (8-2) improve their best start in franchise history since the 1998-99 season.
Jason Kidd collected 11 points, 10 assists and a personal-best 19 rebounds for the 89th triple-double of his career in the Nets' fourth straight loss.
Philadelphia 76ers 92, Portland Trail Blazers 88 Andre Iguodola scored 23 points and reserve Louis Williams had all 19 in the second half, rallying the host Sixers from a 25-point deficit.
LaMarcus Aldridge and Brandon Roy had 25 points apiece for Portland, which was outscored 36-15 in the fourth quarter.
New Orleans Hornets 120, Memphis Grizzlies 118 (OT) David West scored a career-best 40-points, including the game-winning jumper with eight seconds remaining in overtime, sending the visiting Hornets (8-2) to their best start in franchise history.
Spain's Juan Carlos Navarro paced the Grizzlies with 28 points.
Sacramento Kings 123, New York Knicks 118 (double overtime) Kevin Martin scored a career-high 43 points, including four clinching free throws in the final seconds of the second overtime, and the Kings handed the visiting Knicks their fifth straight loss.
Eddy Curry led the Knicks with 27 points and David Lee had season highs of 24 points and 16 rebounds.
Toronto Raptors 110, Indiana Pacers 101 Chris Bosh scored 22 points while Jose Calderon had 15 points and 10 assists, helping the Raptors snap a three-game home slide.
Troy Murphy and Jamaal Tinsley scored 20 points apiece in the Pacers' (3-6) sixth straight loss.
Washington Wizards 105, Minnesota Timberwolves 89 Caron Butler scored a season-high 29 points, and Gilbert Arenas added 27, carrying the visiting Wizards to their third straight win.
Rashad McCants led the Tmberwolves with 19 points.
LA Lakers 103, Detroit Pistons 91 Lamar Odom had 25 points and 15 rebounds, and Kobe Bryant scored 11 of his 19 points in final six minutes of a decisive 41-23 fourth quarter, rallying the host Lakers.
Tayshaun Prince and Rip Hamilton led the Pistons with 16 points apiece.
Golden State Warriors 122, LA Clippers 105 Al Harrington tossed in 27 points while Andris Biedrins had a season-high 23 points and a career-best 18 rebounds, powering the Warriors (1-6) to their first victory of the season.
Tim Thomas led the visiting Clippers with 25 points and Corey Maggette added 22 points and 12 rebounds.