SAN FRANCISCO -- Nobody has ever seen a ghost at AT&T Park, but one sure scared Bryce Harper on Tuesday night.
The Washington Nationals' sensational young outfielder flinched when chasing Gregor Blanco's game-tying triple toward the right field fence in the ninth inning, opening the door for the San Francisco Giants to pull out a 4-2, 10-inning victory on Pablo Sandoval's two-run, walk-off home run.
In what began as a pitchers' duel between Washington's Stephen Strasburg and San Francisco's Matt Cain, the Giants scored once in the ninth and twice in the 10th against the Nationals' bullpen after being limited to one run for the first 26 outs of the game.
Harper, who ran face-first into the right field fence in Dodger Stadium on May 20 chasing a similar ball hit by A.J. Ellis, took the blame for the Nationals' fourth consecutive defeat.
"It's really a play I should have made," he said. "Of course (the chance of another accident) concerns you after you crash into the wall, but I gotta catch that ball."
Instead, the second game of a series matching 2012 division winners went into extra innings. Sandoval's second career game-ending homer -- both of which have come against the Nationals -- touched off yet another game-ending celebration for the Giants, who have won six games this season with their last swing.
Sandoval's homer, measured at 465 feet, capped the Giants' 13th come-from-behind win of the young season. He went deep off Yunesky Maya (0-1), who was called up from the minors earlier in the day.
"We love pressure, man," said Sandoval, whose eighth homer of the season followed a one-out single by Marco Scutaro. "We play better in the bottom of the ninth behind by a run."
Earlier, while Strasburg and Cain were dueling in a 2-1 game through eight innings, Scutaro extended his National League-best hitting streak to 19 games.
Jeremy Affeldt (1-0), the fifth Giants pitcher, threw a perfect top of the 10th. He took the mound with the sellout crowd still buzzing over Blanco's heroics.
Strasburg appeared on the verge of running his career record to 3-0 against San Francisco and beating Cain for the second time as the Nationals held a 2-1 lead with the Giants down to their last strike.
However, Blanco, batting with pinch runner Andres Torres on first and two outs, lashed a shot off closer Rafael Soriano that was over the right shoulder of a retreating Harper.
Just when it appeared Harper might be destined for his second run-in with a wall in nine days, the 20-year-old outfielder cringed as he started to jump for the drive on the warning track, allowing the ball to bounce between him and the fence.
It was the type of cautious approach many have suggested in order for the budding superstar to protect his body in the wake of last week's incident, which resulted in four missed games and bumps and bruised from his knee to his chin. But Harper said he's not listening to those who want him to be more careful, even if it appeared he was in this case.
"That's not the way I play," he said. "If I do, I'll be at Triple-A."
Blanco, who has played right field on occasion for the Giants, sympathized with his rival.
"I know how tough those kinds of balls are in right field," he said. "I knew I hit it hard."
The Nationals, who entered the game with the second-worst team average in the NL, did nothing to help their .227 mark. However, three of their five hits came in the first inning, including RBI doubles by Ryan Zimmerman and Ian Desmond after Harper sacrificed Denard Span into scoring position.
Angel Pagan's two-out single in the second inning scored Blanco with the Giants' first and only run until the ninth.
Coming off his longest outing of the season, an eight-inning homecoming in San Diego last Thursday, Strasburg was pulled after throwing 108 pitches in seven innings. He struck out seven and walked three.
Cain, who had won his previous three starts after going winless in April, rebounded from the two-run first inning to shut out the Nationals from the second through seventh. He stranded the bases loaded in the fourth in his only spot of trouble after the first and finished with seven strikeouts in seven innings, walking two.
The two runs over seven innings improved Cain's May ERA to 3.45 after he'd been cuffed around at a 6.49 clip in his six April starts.
NOTES: Harper also had a sacrifice bunt in the eighth inning. He had only three in 597 plate appearances as a rookie last season. ... Broken hands factored into multiple transactions made by both teams Tuesday. Looking to replace injured RHP Ryan Mattheus, the Nationals called up two pitchers from Triple-A Syracuse, LHP Fernando Abad and Maya, a right-handed starter. Washington sent fifth OF Eury Perez to Syracuse to make room for the second pitcher. ... Mattheus, who suffered a fractured knuckle at the base of his right ring finger when he punched a locker in San Diego on Sunday, went on the disabled list and returned to Washington to determine if surgery is necessary. ... Giants RHP Ryan Vogelsong underwent surgery that included having screws inserted into his right hand after he broke two bones (one in his pinkie finger, the other in the hand below the finger) and dislocated the knuckle below the pinkie when hit by a fastball during a swing Monday night. He was placed on the DL, and his recovery time was estimated at six to eight weeks. ... With a day off Thursday, Giants manager Bruce Bochy announced the team has elected to postpone a decision on Vogelsong's replacement in the rotation. ... The Giants put RHP Santiago Casilla on the DL with recurring pain in his right knee, and they summoned RHP Sandy Rosario from Triple-A Fresno. 1B Brett Pill also came north, taking Vogelsong's spot on the active roster. ... The series finale Wednesday afternoon pits a pair of former first-round draft picks, Washington LHP Gio Gonzalez and San Francisco LHP Madison Bumgarner.