SAN FRANCISCO -- There's always a story behind a walk-off hit. Brandon Belt's tale of triumph was an unlikely one.
The left-handed-batting Belt began the game on the bench, since left-hander Wade Miley started for Arizona. Giants manager Bruce Bochy announced Sunday that platooning at first base with right-handed-hitting Joaquin Arias would be Belt's lot in life for the immediate future.
Such arrangements tend to be subject to change, and Belt took a step toward reclaiming an everyday role by lining a tiebreaking single in the ninth inning off Tony Sipp -- yes, a left-handed pitcher -- to give the Giants a 5-4 victory over the Arizona Diamondbacks.
It would have been easy to imagine that Belt's first Major League game-winning hit saved his sanity, preserved his ego or buoyed his confidence. Yet he insisted that he never felt dismayed after Bochy informed him of the platoon.
"There's a ton of season left," Belt said. "I've been through some [scuffling] before and I've come out better on the other side."
Belt accomplished that shortly after entering the game in the top of the ninth inning as part of a double-switch.
One inning earlier, Buster Posey's two-run homer erased San Francisco's 4-2 deficit. The Giants sustained that momentum in their half of the ninth, which opened with Andres Torres' first-pitch single off Sipp. Torres advanced to second base on Brandon Crawford's sacrifice bunt. Belt then deposited a 1-1 pitch into left-center field, scoring Torres easily and extending the Giants' home winning streak to seven games.
About seven hours earlier, Belt received advice from Bochy and the Giants' hitting coaches while taking extra batting practice. Bochy urged Belt to relax and let the bat do the work. Belt had heard this sort of thing before, but he appreciated Bochy's perspective.
"I think when you get to this point, you feel like you've heard a lot of things," Belt said. "Sometimes you forget it. It's nice to have another set of eyes tell you what they're seeing. It kind of reminds you a little bit of what you need to do and what direction you need to take."
Against Sipp, Belt followed the same approach he always employs in such situations: Look for the fastball and be ready to adjust to an off-speed pitch. He adjusted nicely to Sipp's slider.
Belt indicated that the extra work and advice helped when he faced Sipp.
"I know I felt a lot better," he said.
Bochy wouldn't say whether Belt will start Tuesday against Arizona left-hander Patrick Corbin.
"Whatever happens, happens," Belt said. "If I'm not in the lineup, I'll be prepared to come in again like I did today. But I fully expect to go out there and get better every day. Of course, I want back in there."
Posey made Belt's deed possible by reminding onlookers how he won the National League's Most Valuable Player Award last year. The Giants were five outs away from defeat when Posey followed Pablo Sandoval's one-out single in the eighth with a home run to straightaway center field off David Hernandez. It was Posey's second homer in two days.
The typically stoic Posey allowed himself a fist-pump as he rounded first base.
"I was happy that it went out and the game was tied," said Posey, who also hit a first-inning RBI double.
Hernandez felt frustrated over not being able to set up Posey.
"I feel like if I had been able to throw a curveball, I don't feel like he would have been able to get to that pitch," the right-hander said. "Pretty much eliminated my curveball and my changeup. There was really only one pitch I could have thrown right there. He's still got to hit it and that's what he's paid to do."
Familiar faces sustained Arizona. Ex-Giant Cody Ross hit a two-run, first-inning single, halting the Giants' scoreless-innings streak at 21. Ross also robbed Posey of an extra-base hit with a sliding catch near the right-field corner in the sixth inning. Former A's third baseman Eric Chavez lashed a sixth-inning homer.
But, ultimately, the Giants owned the evening.
"There's no quit in this team, I can tell you that," said Giants starter Ryan Vogelsong, who lasted seven innings. "We fight to the last out. It's fun to watch."
Chris Haft is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.