With his second blown save in 11 chances, Benitez (0-3) spoiled the Giants' prospects for a stirring, hard-fought victory. With 42-year-old left fielder Barry Bonds out of the lineup for a rest (he walked as a pinch-hitter in the 10th), the Giants mustered six hits but broke a 3-3 tie in their half of the 12th without benefit of a hit.
Omar Vizquel drew a leadoff walk from rookie Joe Smith before advancing to third on a wild pitch and Fred Lewis' sacrifice bunt. After Smith nicked pinch-hitter Mark Sweeney with a pitch, Randy Winn cracked a grounder to first base. Delgado stepped on the bag for the second out and threw home accurately, but Vizquel slid feet-first around catcher Paul Lo Duca's tag.
Benitez set the Giants' fourth consecutive loss in motion by walking Reyes on a 3-2 pitch.
"You're asking for trouble walking the leadoff hitter," Giants manager Bruce Bochy said.
Benitez's first balk advanced Reyes to second before Endy Chavez's sacrifice bunt moved the tying run 90 feet from home. The Giants pulled the infield in and got a break as Carlos Beltran grounded out to second base.
Then came Benitez's second balk, which he committed after Reyes' exaggerated feint down the line. All that remained was for Delgado to deliver his fifth career walk-off homer, a drive to right field on a 2-2 pitch.
"He looked for the sinker away," Benitez said. "Hey, whatever you're looking for, if you get it -- he's a great hitter."
Neither Benitez nor Bochy was certain what prompted first-base umpire Bob Davidson to call the initial balk. Nobody had any doubts about the second one.
"I moved," Benitez said.
"He did flinch," Bochy said.
Plate umpire and crew chief Randy March was more expansive about both balks, which Giants general manager Brian Sabean studied on replays after the game.
"The first balk, he started his whole body motion, then stopped. I think he didn't like the sign he got," noted Sabean. "Once the body stops, unless you step off the rubber, you've got to continue. The second balk ... It was a way big-time flinch. Obviously, Reyes startled [Benitez] and he buckled his knees."
Said Benitez, "I focused on him too much."
Bochy said that he wouldn't hesitate to use Benitez in the next save situation -- although the Giants might not have much of a choice.
"We're a little shot in the 'pen," said Bochy, who used relievers Brad Hennessey, Kevin Correia and Russ Ortiz to consume four shutout innings.
The bullpen's excellence -- at least until Benitez arrived -- was among several fruitless highlights for the Giants, who fell into last place in the National League West (they're at .480, 24-26, to Colorado's .481, 25-27).
Tim Lincecum again proved that he's worth the hype, striking out eight in seven innings while yielding only three hits. Lincecum's only mistakes were a fourth-inning fastball that didn't get inside enough, enabling Delgado to swat it for a two-run homer, and a sixth-inning curveball that Beltran whacked for an RBI double.
"You learn more about the whole mind game between hitters and pitchers," said Lincecum, who has started five games. "I'll probably go back home and think about this start, the things I did wrong -- try not to think about those too much, but try to change them."
The Giants nearly lost in the ninth, but with Mets on first and second and two outs, Vizquel dove to smother pinch-hitter Julio Franco's sharp grounder and, while lying on his back, flipped the ball to second baseman Kevin Frandsen, who barehanded the off-target relay while somehow keeping his foot on the bag for the forceout. Earlier, San Francisco made the most of its meager hit total, as Winn and Bengie Molina homered in the first inning before Daniel Ortmeier hit his first Major League home run in the sixth to forge the 3-3 tie.
Ortmeier reported that he didn't recover the ball he struck for his homer, an opposite-field shot that landed in the Mets' bullpen. Fitting, since it was a night of besmirched achievement for the Giants.