SAN FRANCISCO -- Buster Posey hit a walk-off home run on the first pitch he saw from Cincinnati reliever Robert Stephenson in the bottom of the 17th inning, lifting the San Francisco Giants to a 3-2 win over Cincinnati on Friday night in a game that lasted more than five hours and ended at 12:43 a.m. PT.

Denard Span homered for the second straight day and drove in two runs, Eduardo Nunez added two hits and scored, and Cory Gearrin -- the last available reliever in the Giants bullpen -- pitched two innings for the win.

San Francisco had not scored since tying the game in the fifth and only advanced one runner past first base for eight innings before Posey's one-out homer to left. The Giants catcher knew it immediately, too, and flipped his bat before taking off to round the bases for San Francisco's second walk-off win of the season.

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The home run measured 431 feet, Posey's longest of the Statcast™ era.

"Those kind of games, they're must-win," Gearrin said. "You go out there and you battle for that long, a lot of guys put a lot of time and a lot of energy into that game, so to come out with a win is huge. To walk it off like that, with Buster going deep, just kind of seals it for us."

Cincinnati was blanked over the final 15 innings and wasted a strong outing from its bullpen.

"To play 17 and lose, it's a lot different feeling over in the Giants clubhouse than there is in ours," Reds manager Bryan Price said. "Both teams had an awful lot of opportunities to win that game. And no one could come up with the big hit until Posey did there in the bottom of the 17th."

Neither starting pitcher factored into the decision despite strong outings from both. Giants right-hander Johnny Cueto gave up two runs and had six strikeouts over eight innings while throwing a season-high 119 pitches but remained winless against his former club. Scott Feldman of the Reds, who blanked the Giants on four hits May 2, allowed two runs in seven innings.

MOMENTS THAT MATTERED

Missed opportunities: The Reds missed a prime scoring opportunity the top of the 14th after Scott Schebler and Scooter Gennett opened the inning with back-to-back singles. Both runners advanced on a sacrifice before Jose Peraza hit a grounder to Giants shortstop Brandon Crawford, who was playing in. Crawford bobbled the ball briefly then fired a strike to home plate where Posey made a sweeping tag on Schebler for the out. A few moments later, pitcher Bryan Morris wheeled and picked off Gennett trying to scramble back to second base. San Francisco also worked out of a base-loaded situation in the 16th and a two-on, two-out jam in the 17th.

"That pickoff worked well," Morris said. "I felt like [Gennett] was kind of asleep and Brandon felt the same way obviously, so he just back-picked him and I was ready for it."

Small ball: San Francisco took advantage of the speed at the bottom of its lineup and the way Cincinnati was playing back on defense to score the tying run in the fifth. Nunez laid down a picture-perfect bunt near the third-base line and Justin Ruggiano followed with a bunt of his own almost in the same spot. Cueto then nearly reached on a sacrifice bunt before Span hit an RBI single.

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The 17 innings were the second-most played in the history of AT&T Park. The only game that lasted longer came on May 29, 2001, when the Giants lost to Arizona, 1-0, in 18 innings.

WHAT'S NEXT

Reds: The Reds will send right-hander Lisalverto Bonilla (0-0, 7.20 ERA) to the hill Saturday to make his first Major League start since 2014 with the Rangers. Saturday will mark his second big league stint this season after a five-inning relief appearance in April. Bonilla had a 5.61 ERA in five starts with Triple-A Louisville and will be Cincinnati's ninth starter used in 2017. First pitch Saturday is 4:05 ET.

Giants: Left-hander Matt Moore (1-4, 6.52 ERA) will take another stab at getting his season back on track when he faces the Reds for the first time in his career in the third game of this series beginning at 1:05 PT. Moore has been hit hard most of the year, having allowed five runs or more in four of his seven starts.

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