LOS ANGELES -- Reality came crashing down Wednesday night on the Giants, who have been making hopeful noises about climbing back into contention.

Their 6-4 loss to the Los Angeles Dodgers silenced that happy talk for at least one evening.

The Giants led, 4-2, until the Dodgers surged for four eighth-inning runs, the final pair coming on Nomar Garciaparra's homer off Randy Messenger. It might have been a more heartbreaking defeat if this season hadn't featured so much heartbreak already.

Thus, the Giants were better off celebrating what went right.

Tim Lincecum's debut against the Dodgers was an impressive one, as the rookie right-hander surrendered just two hits in six innings. Lincecum allowed two runs (one earned), both generated by leadoff walks to Rafael Furcal.

This may disappoint Giants-Dodgers romanticists, but plunging into the rivalry didn't motivate Lincecum more than usual. At this stage in his career, every outing is of heightened importance for the rookie, regardless of the opposition.

"I don't go in there thinking I have to hump up against these guys because it's a rivalry game," Lincecum said. "Maybe down the line when I'm with the team longer."

Appearing in his first game as a Giant since being acquired from Pittsburgh in the Matt Morris trade, outfielder Rajai Davis displayed the extraordinary speed that was promised. Davis easily reached base safely in the fifth inning when Furcal bobbled his grounder to shortstop, and he collected a bunt single and a stolen base in the eighth inning before scoring.

"He showed us how fast he is," manager Bruce Bochy said of Davis, who led off and played center field. "It was a good debut for him."

Pinch-hitter Kevin Frandsen concluded a big night for the bottom of the Giants' batting order with a seventh-inning RBI single that broke a 2-2 tie. No. 7 hitter Rich Aurilia singled twice and scored twice. Eighth-place hitter Omar Vizquel lashed three doubles and twice drove home Aurilia before scoring on Frandsen's hit. "I love those situations, whether you're starting or pinch-hitting, with the winning run on the line," said Frandsen, who poked a 2-2 pitch into center field off Dodgers starter Mark Hendrickson with two outs.

Giants left fielder Barry Bonds remained frozen at 754 home runs, one behind all-time leader Hank Aaron, after going 0-for-3 with an intentional walk. But Bonds drew that walk with Davis on third base and one out in the eighth inning. It helped generate the Giants' final run, as Bengie Molina rapped an RBI single to right field off Dodgers reliever Jonathan Broxton.

Then the Giants' evening soured. Furcal's bunt single opened the Dodgers' surge in the eighth against Vinnie Chulk. Facing Steve Kline, Juan Pierre added an infield single on a slow grounder to shortstop, with Furcal reaching third as Vizquel's throw skipped past first baseman Mark Sweeney. It was only Vizquel's sixth error of the season.

Messenger (1-3) relieved Kline and coaxed a comebacker from Russell Martin after Pierre stole second base. But Luis Gonzalez singled past third base to score Furcal and Pierre. Garciaparra then yanked a 1-0 pitch into the left-field pavilion for his fifth homer of the season.

Messenger declined to comment afterward, but his teammates rallied around him.

"Ever since he came over in that trade, he's been unbelievable for us," Frandsen said. "People need to realize what he's done the whole time."

Indeed, Messenger owns a 2.75 ERA overall, 2.83 with the Giants since joining them from Florida in the Armando Benitez deal. But the right-hander has sagged lately, allowing six runs in 3 2/3 innings spanning his last three outings.

"His command's not what it was," Bochy said. "The slider's not quite as sharp and he's getting balls over the heart of the plate."

More than just the defeat stung the Giants. Aurilia left the game with a mild pull in his right hamstring, which he felt as he slid home in the fifth inning. He left the game afterward. Second baseman Ray Durham tweaked his back but played the entire game. Asked if he'd need a day or two to rest, Durham said, "Hopefully not," although Bochy said that Frandsen is likely to start at second in Thursday's series finale.