SAN FRANCISCO (AP) -- The San Francisco Giants pinned their hopes on Jake Peavy to provide new life to a beat-up rotation and a lineup searching for a lift.
It was a disappointing debut for the right-hander a day after being traded by the Boston Red Sox, and he dropped his 10th straight decision in a 4-3 defeat to the Dodgers that sent the rivals back to Los Angeles with a sweep and the NL West lead.
Still searching for runs, the Giants were outscored 17-4 and lost for the 19th time in their last 25 home games. They have lost four straight overall.
"It's going to be important to put it behind us," manager Bruce Bochy said. "We have to regroup."
Carl Crawford hit an RBI triple to back Hyun-Jin Ryu's third straight victory as the Dodgers grabbed momentum in the division as August approaches.
Ryu (12-5) moved within two wins of his rookie total last year and improved to 4-1 in five outings at AT&T Park, where in one dominant weekend the Dodgers made quite a statement to take over the NL West's top spot.
"You make enough of a statement by winning three games," manager Don Mattingly said. "Obviously it's something. That's all it is at that point because you have a lot of baseball to play. We're going to see these guys again. They're not going anywhere."
Peavy threw a pair of wild pitches in the fifth as the Dodgers went ahead on Hanley Ramirez's RBI single ahead of Crawford's triple to the corner in deep right field.
"I was comfortable tonight. I've played against the Dodgers quite a few times and I've played in this ballpark," Peavy said. "It was fun being on the right side. I just hate the way it turned out. I think I can get much better. I expect to get much better."
Again, Peavy suffered from a lack of run support, getting three or fewer runs of support for the 11th straight outing.
San Francisco was swept in the rivalry for the first time since June 24-26, 2013, at Dodger Stadium. The last Dodgers sweep at AT&T Park came July 27-29, 2012.
"It was great. To come out of here with a 1 1/2-game lead, especially coming into it with a 1 1/2-game deficit, obviously best-case scenario," first baseman Adrian Gonzalez said.
Buster Posey hit a solo home run in the fifth for San Francisco's first extra-base hit since Hunter Pence doubled in the ninth inning Wednesday at Philadelphia - the Giants' first three-game stretch without an extra-base hit since May 30-June 1, 2002.
Ryu struck out seven in six innings and improved to 8-2 in 11 road starts. Kenley Jansen followed scoreless innings by J.P. Howell and Brian Wilson for his 30th save.
Peavy (0-1) pitched a day after being traded from the Boston Red Sox to the Giants for a pair of minor league pitchers, reuniting him with former manager Bruce Bochy. Peavy pitched for Bochy and the Padres in the playoffs in 2005-06.
That understanding sure helps.
Bochy stuck with the right-hander to get through the sixth after he allowed a leadoff walk to Juan Uribe. Peavy drew regular roars from a lively sellout crowd at AT&T Park as fans found plenty to cheer for after a frustrating few days.
"I am high strung out there and that's something I really can't change," Peavy said. "I'm going to give you everything I've got. I can't let my emotions get the better of me."
He allowed six hits and four runs - three earned - struck out five and walked two in six innings.
Peavy dropped to 14-3 with a 2.28 ERA in 26 starts against Los Angeles, including a three-hitter last Aug. 25 at Dodger Stadium in which he struck out five and walked one.
Second baseman Dan Uggla committed two errors, including one that helped tie it early after he scored the game's first run in the bottom of the third. Uggla's fielding error leading off the top of the fourth allowed Ramirez to reach and Uribe later singled in the tying run.
"It's a tough game sometimes," Bochy said. "You're going to make errors."
NOTES: Posey homered on a 3-0 pitch for the first time in his career. ... Former Giants closer Wilson drew cheers during pregame warmups, then boos for the beard when the Los Angeles reliever jogged out for the bottom of the eighth. ... Madison Bumgarner (12-7) pitches when San Francisco begins a three-game series at home with Pittsburgh on Monday night.