It was a little more than midway through the third quarter and the Blazers were in the midst of a 17-6 run that would seal their 107-96 victory Thursday night.
Kobe Bryant missed a 3-point attempt and Marcus Camby pulled down the rebound before hurling the ball downcourt to Wallace, who leapt for a stunning windmill dunk that put Portland up 70-66.
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"I think that was the game-changer," said Wallace, who joked that he only performed the highlight-reel dunk because teammate LaMarcus Aldridge promised he'd make one, too.
"Watch out for L.A.'s windmill next," he laughed.
Wallace finished with 31 points, including the windmill, while Aldridge added 28 points and 10 rebounds for his first double-double of the season. Portland, which led by as many as 14 points, had just four turnovers despite pushing the tempo for the entire game.
The Blazers sit atop the Western Conference at 5-1 -- their lone loss coming on New Year's Day at the Clippers.
Bryant scored 30 points despite a torn ligament in his right wrist, and Andrew Bynum had 21 points and 12 rebounds for the Lakers, who have had trouble at the Rose Garden with losses in 11 of their last 13 games there.
"They (the Blazers) played a heckuva game," Lakers coach Mike Brown said. "Portland came out in the second half and pushed the pace, and we came apart."
Los Angeles went 0 for 11 from 3-point range. It was the first time that the team had a game without a 3-pointer since November 2003.
The Lakers, who fell to 4-4, were coming off a 108-99 home victory over Houston on Tuesday. Bynum, who was suspended for the first four games of the season, had 21 points and 22 rebounds against the Rockets -- the first 20-20 game of his career.
The Blazers were coming off a 103-93 victory at Oklahoma City, another statement win to open the lockout-shortened season.
"It's still early," Aldridge said. "It's always good to get off to a quick start, especially in a short season. But we know it's a process."
The Lakers were without Josh McRoberts, who sat out a second straight game with a strained big toe on his left foot.
Blazers coach Nate McMillan promised that Portland would run against the Lakers, and the result was a frenetic pace from the start. Pau Gasol's tip-in gave Los Angeles their biggest lead of the first half at 28-21.
The Blazers closed the gap and Jamal Crawford's jumper and free throw put them up 36-35 with just over 8 minutes to go in the half. The lead was short-lived but Portland stayed close.
Los Angeles shot 61 percent from the field, but led just 56-52 at the half. Portland shot 43 percent. Both teams were even at 46 percent in the end.
The Blazers trailed 60-59 early in the third quarter before Wallace made a layup and a free throw early to spark a 17-6 run that included his dunk. The surge was capped by Wesley Matthews' 3-pointer that made it 76-66.
Crawford made a 27-foot 3-pointer as time ran out in the third to put Portland up 84-74.
"They came out in the second half and just beat us down the court in transition and that was it," Bynum said. "We've got to get back on D, that's huge for us."
Wallace appeared to seal it with a fast-break layup past falling Lakers guard Steve Blake that made it 96-83 with 6:39 left.
Bryant was asked after the game about the storyline of losses in Portland.
"It drives me crazy," he said.
The Blazers travel to Phoenix to play the Suns on Friday night, while the Lakers host Golden State at Staples Center.
The Lakers have won seven of the last eight meetings with the Blazers at Staples Center. ... Blazers G Matthews' dad Wes played for the Lakers from 1986-88 during his nine-year NBA career. ... Oregon Ducks running back Kenjon Barner had a courtside seat. ... A fan in the crowd had a sign reading "Tonight I'm against World Peace" -- a jab at Metta World Peace, formerly Ron Artest. ... Brown insisted Bryant wasn't having trouble physically. "He was fine. Shooting 13 of 24 is pretty good for a 2-guard." ... The Lakers outrebounded the Blazers 47-39.