SAN FRANCISCO - The uprising required three improbable hits from three improbable sources. But in the ninth inning Monday night, everything fell into place for the Mets.

And because of it, Jonathon Niese became a winner for the first time since May 9, the beneficiary of a late rally that gave the Mets a 3-0 win over the Giants.

Niese cruised through eight scoreless innings, then watched batterymate Johnny Monell deliver the winning hit, a two-run double that reached the rightfield fence and sent the Giants to their seventh straight defeat.

"It felt great just being able to come through for the team," said Monell, who didn't try to hide the extra satisfaction after beating the team that had drafted him.

Monell delivered the deciding hit in perhaps the most unlikely rally of the season, as four Mets produced hits in the ninth after falling behind 0-and-2.

With the game still scoreless, the slumping Michael Cuddyer had a leadoff single against reliever Sergio Romo. Kirk Nieuwenhuis followed with a double in his first game since being reacquired by the Mets.

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That set the table for Monell, who was in the starting lineup for a second straight day only because the struggling Lucas Duda was benched and the Mets needed another lefthanded hitter in the lineup. Two batters later, Juan Lagares had an RBI single to make up for a baserunning gaffe an inning earlier.

Jeurys Familia worked a perfect ninth for his 23rd save in 25 chances.

For all the doom and gloom that accompanied the Mets (43-41) on their six-game West Coast road trip, they already have clinched at least a split. "To get off to this start on this road trip is huge," Terry Collins said.

Perhaps just as important was finally rewarding Niese (4-8), who needed only 81 pitches to log his eight scoreless innings. The lefty outdueled Giants righty Chris Heston, who no-hit the Mets on June 9 and bowed out Monday night after 71/3 scoreless frames of his own. The Mets have not scored a run in 161/3 innings against him this season.

"We had a good feeling they'd be aggressive today, which they were," said Niese, who extended his streak of quality starts to six.

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Niese encountered his first hint of resistance in the sixth. He allowed a leadoff single to Joaquin Arias, who advanced on a sacrifice bunt by Heston. With two outs, Niese walked Edire Adrianza and Matt Duffy to load the bases but got Buster Posey to hit a sharp grounder to third, and Daniel Murphy had plenty of time to retire the plodding Posey.

Heston didn't come close to repeating his no-hit feat this time as Ruben Tejada ripped a first-inning single. Still, he took a shutout into the eighth inning, even though he committed two of the Giants' three errors.

The Mets' inability to take advantage of some breaks emerged again in the eighth, when Lagares failed to advance on an apparent bloop single to shallow left, getting forced at second. But one inning later, the Mets couldn't miss.

Monell remains friends with most of the Giants, including Heston, his once-time minor- league roommate. But those relationships took a back seat to the moment, which Monell seized by hammering Santiago Casilla's fastball.

"At the end of the day,'' Monell said, "you've got a job to do."