It was San Francisco's ninth loss in its past 10 games against New York.
The Giants not only wasted a chance to gain ground in the National League Wild Card race -- they are 1 1/2 games behind first-place Colorado, which fell to Florida -- they lost the edge created by Wednesday's stirring 10-inning victory over Los Angeles.
Blame Thursday's off-day, which left the Giants idle when they ideally should have been playing, some suggested.
"It's hard to ride that momentum when it's not the next day," left-hander Barry Zito said.
Then again, it wasn't as though the Giants faced a pitcher reminiscent of Tom Seaver, Nolan Ryan or any of the storied Mets from yesteryear. Their chief tormentor in the opener of their three-city, 11-game sojourn was rookie Bobby Parnell (3-4), who made his second Major League start.
Parnell lasted only 2 1/3 innings before exhausting his pitch limit in his previous start, at San Diego on Saturday. This time, he maintained enough command to last six innings. He allowed three singles and struck out seven while walking none.
Center fielder Aaron Rowand, who struck out twice against Parnell and three times overall, explained the challenge the right-hander presented.
"He was throwing 97 [mph] with a hard slider," Rowand said, adding that Parnell caught him "in between" pitches. "You'd get on his fastball because he throws hard, and he'd break out the slider. You'd sit back a little bit, and he'd throw the fastball by you."
The Giants drew just one walk after coaxing a season-high nine on Wednesday, but manager Bruce Bochy didn't fault his hitters for not sustaining their patience.
"[Parnell] threw strikes," Bochy said. "It's not like we chased a lot of pitches."
The Giants didn't authoritatively connect with a lot of pitches, either. As Bochy pointed out, two of their hardest-hit balls came after they put runners on first and second with one out in the eighth. Both traveled directly toward Mets infielders. Eugenio Velez's one-hop smash to first base forced Fred Lewis at second before Freddy Sanchez's sharp grounder to third ended the threat.
But Bochy made no excuses for the Giants' sixth shutout defeat of the season.
"There's no getting around it. We have to get these bats going," he said.
Unfortunately for the Giants, Bochy, general manager Brian Sabean and the coaching staff have spent countless hours trying to devise ways to enliven the offense.
"We have discussed lineups -- mixing it up, [changing the batting] order, all that -- quite a bit," Bochy said.
The Giants' absence of offense in their first game at Citi Field was nothing new for Zito, who has received the Major Leagues' lowest run support this season. Zito (8-11) allowed all of New York's runs and five hits while lasting two batters into the sixth inning.
Zito would have had to be perfect just to forge a tie, and perfection eluded him with the first batter he faced, as Angel Pagan hit the Mets' first leadoff homer of the season. That represented a dubious start for the Giants, who trail every Major League team in home runs except for ... the Mets.
"Tip your hat to Pagan right there," Zito said. "That was a good pitch, a fastball up and in. He just turned on it and dropped the barrel [of the bat]."
The Mets widened their lead to two runs in the fourth on Jeff Francoeur's RBI double, a line drive directly over Rowand's head that momentarily froze him before he broke for it.
"The balls that are hit right at you are the toughest ones to read and gauge depth on," Rowand said. "You're taught to hold your ground and not give one way or the other until you can read it. By the time I read it was going over my head, it was too late."
Zito vanished in the sixth after Luis Castillo walked and moved to third on David Wright's double. Zito started straight for home plate and didn't look at Bochy when the manager removed him for Justin Miller, who allowed Gary Sheffield's sacrifice fly.
But Zito expressed no annoyance with Bochy, instead criticizing himself for dangling the 0-2 pitch that Wright hammered.
"I just left [it] over the middle," Zito said.