SAN FRANCISCO -- Barry Bonds' first-inning home run and Armando Benitez's scoreless ninth inning provided sturdy bookends Wednesday night for the Giants.

But the Giants had little to stuff between them.

Bonds' 735th career homer provided scant consolation for the Giants, who lost, 5-3, to the San Diego Padres as Adrian Gonzalez snapped a 3-3 tie with a two-run, two-out homer in the eighth inning.

Marcus Giles singled with one out in the eighth off Brad Hennessey (0-1), who was replaced by left-hander Jack Taschner with two left-handed batters due up next. Taschner retired the first, Brian Giles, before Gonzalez hammered his 0-1 fastball onto the right-field arcade. Taschner pounded his glove in despair as he watched the ball vanish.

"I completely blew that spot. I was trying to go down and away," Taschner said. "When you miss over the heart of the plate, that's going to happen. I not only let myself down but [also] the team down with one pitch. Mistakes like that don't get missed very often."

Unfortunately for the Giants, they repeated this transgression. Matt Cain, who entered the game with glittering career numbers against the Padres (3-0, 1.64 ERA, .133 opponents' batting average), seemed poised to sustain that dominance by allowing two hits in the first four innings. That changed in the fifth inning, when he yielded Khalil Greene's leadoff home run and Marcus Giles' two-run homer.

Cain doomed himself in the fifth when he issued his only walk of the evening, a one-out pass to Terrmel Sledge. Chris Young struck out while trying to sacrifice Sledge ahead, but that didn't matter when Cain fired a 1-0 fastball down the middle that Giles redirected into the left-field seats. Like Taschner, Cain immediately displayed his frustration by squatting and grimacing as the ball flew away.

"I was just upset that I got beat on that pitch," said Cain, who lasted six innings. "It was a missed location so bad; that bothered me the most."

Benitez provided encouragement with an outing that mirrored his Spring Training effectiveness -- and actually exceeded it, by one standard. A telecast's velocity readings clocked Benitez's fastball in the mid-90-mph range, significantly harder than he threw during the Cactus League.

Benitez yielded Kevin Kouzmanoff's double and walked Sledge with two outs, but ended the inning by coaxing pinch-hitter Russell Branyan's popup.

Earlier, Bonds delivered the kind of multifaceted effort that was typical of him when he was younger and spryer.

With two outs in the first inning, he lofted Young's 2-2 pitch into the left-center-field seats, leaving him 20 homers behind all-time leader Hank Aaron and setting off a chain reaction of factoids: Young became the 435th pitcher to surrender a Bonds homer; Bonds vaulted atop the franchise's runs-scored list in San Francisco annals with 1,481, surpassing his godfather, Willie Mays; Bonds hiked his career home run total against San Diego to 86, his most against any team.

Bonds also ended the Padres' third by hustling toward the left-field line to make a basket catch of Brian Giles' popup that might have scored Marcus Giles from first base. Bonds briefly reached for his left hamstring, crouched in front of the Giants' dugout in apparent discomfort and headed immediately for the clubhouse. But he returned later that inning to ground out to second base and played the entire game.

Bonds shrugged off his discomfort, citing "age," although manager Bruce Bochy answered affirmatively when asked whether Bonds "tweaked" his leg.

"He said it got better, but he was pretty tight there at the end," Bochy said.

The Giants added a third-inning run on Dave Roberts' one-out triple and Omar Vizquel's single, but squandered a chance for more when Bengie Molina flied out to end the inning with the bases loaded.

After the Padres powered ahead, San Francisco pulled even in the sixth. Ray Durham singled leading off, stole second base, moved to third on Rich Aurilia's flyout and scored on Pedro Feliz's two-out single.

That ended the Giants' offense as San Diego's formidable bullpen trio of Cla Meredith (1-0), Scott Linebrink and Trevor Hoffman, who notched his 483rd career save, combined to allow one hit in the final three innings. Bochy refused to admit that watching Hoffman, who preserved countless leads for him while he managed the Padres from 1995-2006, caused any emotional conflict: "That's all behind me as far as that."

The Giants could only hope their futility was behind them after falling to 0-2 for the first time since 1996. They haven't started 0-3 since 1984, when they finished 66-96.

Cain tried to remain optimistic.

"Us as pitchers kind of let the position players and hitters down. That will come around," he said. "We got beat today on a couple of long balls. It's something we feel won't happen a lot with us. We feel we're a good staff and we're going to help ourselves out."