Matt Cain, Buster Posey and Pablo Sandoval celebrate the NLDS victory.
Giants catcher Buster Posey broke open the deciding game of San Francisco's divisional playoff series with a fifth-inning grand slam, giving the Giants a six-run lead and driving Reds starter Mat Latos from the game.
The home run was the deciding moment of the game that was filled with tension down to the last out.
Relief pitcher Sergio Romo called Posey's hit unreal. "That guy's definitely the MVP of our team. We believe he's the MVP of the league. We wouldn't be here without him, that's for dang sure. He's the one that's been the face of the team all season long," Romo said after the game.
"I don't think anybody gave up,'' Posey said of the team as they faced the tough odds of pulling off a sweep in Cincinnati.
The Reds would cut the lead in half by the end of the sixth, and in each of the last four innings had a chance to tie the game with runners on bases, but failed each time on the way to a 6-4 Giants win.
"We could go up against anybody at any time,'' shortstop Brandon Crawford said. "Being down 2-0 and coming back and winning three at their place, it's an unbelievable feeling.''
The win puts the Giants back in the National League Championship Series for the first time since 2010, when they won the World Series.
They will face either Washington or St. Louis. That series is tied 2-2 with a deciding game Friday. If the Cardinals win the Giants will have home field advantage and start the NLCS Sunday at AT&T Park. If the Nationals win, the Giants will fly to D.C. for a Sunday start on the road.
The Giants were poised to jump out to a first-inning lead against Mat Latos, but failed to capitalize on back-to-back singles by Marco Scutaro and Pablo Sandoval. Giants starter Matt Cain also struggled in the first, giving up a single to Zach Cozart and walking Joey Votto, before getting both Ryan Ludwick and Jay Bruce to go down swinging to end the threat.
Latos and Cain both settled down, each facing the minimum over the next two innings, with Cain overcoming an error at third by Sandoval and getting some help from Gregor Blanco, who made a diving grab of Cozart's sinking liner to left to end the third inning.
The game remained scoreless until the fifth, when Blanco poked a single through the left side of the infield to lead off the inning. Brandon Crawford followed, working the count to 2-0, forcing Latos to get a little more of the plate than he would've liked. Crawford pounced, ripping a triple into the right-field corner and scoring Blanco to put the Giants up 1-0.
Two batters later Crawford would come home on a high chopper to short by Angel Pagan. Cozart fielded it cleanly, but bobbled the ball on the transfer, putting the Giants up 2-0 with Pagan at first. A walk to Scutaro and a single by Sandoval loaded the bases for MVP candidate Buster Posey.
Posey rose to the moment, jerking a 2-2 fastball high into the Cincinnati sky. By the time the ball came to rest in the left field bleachers, the Giants were up 6-0.
Sam LeCure came on in relief of Latos, getting the last two outs of the inning, but by then the damage was done.
Despite a six-run lead, Cain faltered in the bottom of the inning, hitting the lead-off batter with a pitch and giving a up a single, to set the stage for a two-run double by Brandon Phillips.
The Reds chipped away at the Giants lead again in the sixth, when Ryan Ludwick hit a lead-off home run to make the score 6-3. Jay Bruce followed that with a walk, and the Scott Rolen drove a single to center to give the Reds runners on first and third with nobody out.
But Giants manager Bruce Bochy stuck with Cain, who was saved from further damage by a strike 'em out, throw em double play. Reds catcher Ryan Hanigan went down looking on a pitch that barely grazed the strike zone, and Posey gunned down Jay Bruce, who was heading for third.
It would be Cain's final batter of the game, as he gave way to George Kontos, who would get Drew Stubbs to ground out to end the inning, and preserve the Giants 6-3 lead through six.
The Reds threatened again in the seventh, as Ludwick came to the plate to face Jeremy Affeldt with two on and two out. Ludwick fouled off a number of pitches on his way to a full count, before tapping a weak grounder back to the mound which Affeldt scooped up and underhanded to Brandon Belt at first for the final out of the inning.
In the eighth the Reds would bring the tying run to the plate for the third inning in a row, and once again the Giants would wiggle free. Dioner Navarro came up with two on and two out to face Sergio Romo, and punched a duck snort to center field. But Angel Pagan came charging and took a knee to get low enough to slide his glove underneath the ball just inches from the ground.
The Reds would bring the tying run up yet again in the ninth, as Sergio Romo walked Cozart and gave up a single to Votto. Ludwick followed with a single that plated Cozart and trimmed the lead to 6-4.
Bruce was next, and battled Romo through a 12-ptich at-bat that ended with a harmless flyball to left, leaving the game and the season in the hands of Scott Rolen, who went down swinging on a 1-2.
The Giants rushed the mound where they hugged and huddled before a stunned Reds crowd. "It was a spectacular moment,'' outfielder Hunter Pence said.