Blanco seized that chance by bunting for a 10th-inning single that scored Melky Cabrera with the ultimate winning run as the Giants outlasted Philadelphia, 6-5.
The Giants maintained their 2 1/2-game lead over second-place Los Angeles in the National League West with one of their most significant victories in what's becoming a compelling season.
They climbed to a season-best 12 games over .500 (53-41) while improving to 4-1 on their challenging trip to face the Braves and Phillies (call it the 2010 postseason revival). San Francisco is 7-1 since the All-Star break, having thrived during that stretch in multiple ways.
"That's why baseball is fun," Blanco said. "You win on a bunt today. Tomorrow we can win with pitching. Or we can win with more home runs. That's why we're playing so well this year. Everybody's trying to contribute. It's not [just] Melky or Posey."
Asked if the Giants were in the midst of playing their best baseball, right-hander Matt Cain hesitated before answering. He didn't quite say yes, but his response sounded more affirmative than negative.
"It seems like we're doing a lot of things right right now," Cain said. "A lot of the guys are finding ways to pick each other up. I don't know if it's our best baseball, but I know that we're playing really well and we have to keep that going. We can't really think about it if it is our best baseball. We have to keep doing what we're doing and get the job done."
Saturday, San Francisco got it done with equal doses of power and pluck.
Preceding Blanco's bunt, they homered three times. Cain delivered the first one in the top of the third inning, setting up a historic moment in the bottom of the third when he yielded a homer to his Phillies counterpart, Cole Hamels. It marked the first time that starting pitchers had homered off each other since May 18, 2002, when Atlanta's Kevin Millwood and Colorado's Denny Stark did so at Coors Field. Moreover, no pair of starting pitchers had gone deep against each other in the same inning since May 14, 1990, at Dodger Stadium, when Montreal's Kevin Gross and Los Angeles' Fernando Valenzuela played can-you-top-this.
Cain assumed that Hamels, who had never homered, would strive to match his feat.
"I'm thinking that he's probably going to try to do the same thing, because when you give up a home run to the pitcher, it's probably the most frustrating thing you can do," Cain said.
Posey equaled a career high with four hits, including a two-run homer in the third inning that gave the Giants a 3-1 lead. After Philadelphia's Ryan Howard erased a 4-2 Giants edge with a three-run homer in the sixth, Cabrera christened the eighth with his 10th homer of the year to forge a 5-5 tie.
"That put the momentum back on our side," Cain said.
Any advantage the Giants might have enjoyed was tempered three batters later when Posey, who had doubled, advanced to third on a groundout and suddenly charged home on a 1-1 pitch to Blanco. Instead of squaring to bunt, Blanco barely budged. Posey, who assented with a reporter's question about feeling a "sense of dismay," was slightly more than halfway home when he skidded to a halt and scrambled back to third base, only to be thrown out easily.
Cain, who allowed five runs and only five hits -- though three were homers -- kept the Giants in contention by finishing his effort with a scoreless eighth. Javier Lopez and Sergio Romo blanked Philadelphia in the ninth. After Cabrera drew a walk from Phillies closer Jonathan Papelbon to lead off the 10th and raced to third on Posey's single, the scene was set for Blanco, who was told on the bench to consider bunting -- this time in a non-squeeze situation.
Batting with one out, Blanco worked the count to 3-1. That's when his inner voice, prompted by the advice he received moments earlier, spoke again: "I said to myself, 3-1, this is it. The right moment. Bunt it."
Blanco pushed his bunt toward first base. Howard charged and fielded it, but had no play at home on the speedy Cabrera or on Blanco, who had rushed past him.
Then came another act of redemption. Santiago Casilla, who had blown five of his previous eight save opportunities, survived a one-out walk to preserve the lead and record his 24th save. Casilla benefited from a chat with pitching coach Dave Righetti, who told the right-hander that he was relying too much on his fastball.
"You make a mistake here, you have to pay," Casilla said. "And I paid."
The experience apparently was worth it for Casilla and, by extension, the rest of the Giants.
"These are character-building games," manager Bruce Bochy said.