It concluded a two-run rally that halved a 4-0 deficit. It gave the Giants impetus entering the sixth inning, when Juan Uribe and Aubrey Huff each belted titanic two-run homers -- Uribe's landing in the center-field "Pirates" topiary, and Huff's clearing the right-field stands.
The trio of long balls matched a single-game season high for the Giants, whose 40 homers entering the game ranked 13th in the National League. Their unusual display of power enabled them to record their largest comeback victory of the year.
Huff's home run, which came about 20 feet short of landing in the Allegheny River, was the most impressive-looking. But even he said that Whiteside's shot bore the biggest impact.
"I think Whitey's homer really got us going," Huff said.
That's because Whiteside's homer seemed to reverse the Giants' fortunes, which began sinking after rain delayed the game's first pitch for two hours and 55 minutes. They grounded into three double plays in the first five innings. The last of those, struck by Aaron Rowand, came with runners at the corners and generated a run, but it deflated San Francisco's momentum -- until Whiteside, who followed Rowand to the plate, connected.
"Huge at-bat," manager Bruce Bochy said. "Now you're within two [runs]. That gives life to any club."
It definitely enlivened the Giants, who opened their two-city, seven-game trip with their seventh victory in 10 games.
Jonathan Sanchez (4-4) weathered Pittsburgh's four-run second inning and retired 13 consecutive batters from the second through sixth innings. For Sanchez, this game was, according to Huff, "a little bit of payback for his one-hit loss in San Diego."
"That's where he's grown as a pitcher," Whiteside said. "He came right back out and went at them. Give him credit for keeping us in the ballgame right there."
First baseman Buster Posey, whose misplay of Duke's two-out grounder made all of Pittsburgh's runs unearned, atoned by doubling off the right-field wall to open the fifth inning and singling to deep shortstop to prolong the sixth in front of Huff's homer.
"Stuff like that is going to happen sometimes," Posey said of his first error in six games. "It's part of the game. You've got to keep on chugging."
Such perpetual motion is outfielder Andres Torres' specialty. Moved from right field to left as part of a handful of moves by Bochy to strengthen the Giants' defense in the ninth inning, the speedy Torres flung himself after Ryan Doumit's line drive to make a sparkling catch for the first out, stopping a rally before it started.
Brian Wilson personally took care of the rest by striking out the next two Pirates for his 100th career save. The right-hander joined Robb Nen (206), Rod Beck (199), Gary Lavelle (127) and Greg Minton (125) in the triple-digit club among the franchise's San Francisco-era relievers.
Wilson, who recorded his 14th save in 15 chances, said he was vaguely aware before the season began that he was approaching the milestone.
"It's not something I think about every day," Wilson said. "It's nice to harbor on for about five or 10 minutes, then it's back to work tomorrow."