LOS ANGELES -- Jake Peavy helped the team with the most series victories in the majors this season to take one from a club that hadn't lost one in 2½ months.
The Red Sox, who won their 26th series, were the first team to capture one from the Dodgers since June 14-16, when Pittsburgh took two of three. But Los Angeles is 46-12 since June 22.
"Tonight was a very big night for us, and we knew that," Peavy said. "We had to come in here and play a very good team that hadn't lost a series in quite a while. You watch them on tape, then watch them get ready for a game, and you see why they've been so successful.
"They've been on an incredible run, but we're a good ballclub as well, and this shows the caliber of ballclub that we are," he added. "We're on the same level with those guys. I knew the day I walked into this clubhouse what we had here. And every guy, man for man, knows that we're capable of playing with anybody on a given day. It's just up to us to be prepared to do that."
Jarrod Saltalamacchia, Shane Victorino and Mike Napoli homered for the Red Sox on the anniversary of the blockbuster nine-player trade in which the Dodgers acquired Adrian Gonzalez, Carl Crawford, Josh Beckett and Nick Punto from Boston.
Gonzalez hit his 17th homer, driving an 0-2 pitch to center field with one out in the fourth for the Dodgers' first hit after the Red Sox staked Peavy to a 3-0 lead.
"I don't like facing Adrian Gonzalez," said Peavy, Gonzalez's teammate for three-plus seasons in San Diego. "He's an extremely good player, but that can't happen there on 0-2. I've got to make a better pitch. I was trying to change his eye level way higher than it was. When I played with him, he hit about 40 a year, so I've seen that multiple times. And it doesn't feel good being on the receiving end."
The victory enabled the Red Sox to regain sole position of first place in the AL East and put them a game ahead of the Tampa Bay Rays, who lost 3-2 to the Yankees in 11 innings.
The Dodgers maintained their 9½-game lead over Arizona in the NL West, following the Diamondbacks' 9-5 loss at Philadelphia.
"I think this was a good little lesson for us," manager Don Mattingly said after watching his team get just four runs and nine hits combined against Peavy, John Lackey and Jon Lester in 24 1/3 innings.
"If we're going to be fortunate enough to do anything and get anywhere, that's the kind of pitching we're gonna see. You're gonna see teams with veteran pitching that knows what they're doing, and you better have a game-plan when you walk up there."
Peavy (10-5) threw 111 pitches in his 300th big league start, going the distance for the 16th time while striking out five and walking one. The right-hander is 2-1 with a 3.31 ERA in five starts since Boston acquired him in a trade from the Chicago White Sox.
"We got ahead of most guys and dictated the count. You have to do that when you're going against a lineup as talented as they are," Peavy said. "Fortunately we were able to put a good game plan together."
Chris Capuano (4-7) gave up three runs and six hits through five innings in his first career appearance against Boston. The 35-year-old left-hander, who was born in Springfield, Mass., has gotten through the seventh inning in only one of his 18 starts this season.
Dustin Pedroia was credited with an infield hit in the first inning on a missed call by umpire Mark Carlson, who ruled him safe after shortstop Hanley Ramirez charged in on Pedroia's grounder and Gonzalez scooped up the low throw in time.
Victorino, who had doubled with one out before Pedroia came up, scored on Napoli's ground-rule double to center. But Capuano minimized the damage by getting Will Middlebrooks to ground into a double play, after loading the bases with a two-out intentional walk to Jonny Gomes.
Pedroia made it 2-0 in the third with a sacrifice fly. Xander Bogaerts, playing in his fourth major league game, got his first RBI with a fourth-inning double, and the Red Sox increased the margin to 6-1 with Saltalamacchia's two-run homer in the sixth and Victorino's solo shot in the seventh -- both off rookie Chris Withrow.
Napoli capped the scoring in the ninth with his 16th home run, a two-run shot against Brandon League.
"You never want to lose two games in a row," Crawford said. "But we've just got to get back to doing what we do, put these two games behind us real quick and get back to our winning ways."
The Dodgers are 94-72 since the trade, and the Red Sox are 84-82. ... RHP Clay Buchholz began a minor league rehab assignment on Sunday with Class A Lowell against Hudson Valley and faced seven batters, giving up three runs -- one earned -- along with a hit and three walks on 38 pitches. He hasn't pitched for the Red Sox since June 8 because of a neck strain. ... Peavy is the 25th pitcher to make at least 300 starts in the majors. His only relief appearance was with the White Sox on June 25, 2001. ... The Dodgers finished their interleague schedule 12-8, their first winning record against AL clubs since 2004 (10-8). The Red Sox, who don't complete their interleague slate until Sept. 24-25 at Colorado, are 13-5 against NL teams.