SAN FRANCISCO -- Marco Scutaro drew a bases-loaded, four-pitch walk from Brayan Villarreal with two outs in the ninth inning Tuesday, completing the San Francisco Giants' rally for a 3-2 win over the Boston Red Sox.
It was a losing day all the way around for the Red Sox, who learned before the game that pitcher Ryan Dempster was suspended by Major League Baseball for five games for hitting the New York Yankees' Alex Rodriguez with a pitch Sunday night. Dempster chose not to appeal the suspension, which runs through Sunday.
Red Sox phenom Xander Bogaerts made his major league debut as the starting shortstop and went hitless in three at-bats. The 20-year-old was given a golden opportunity to produce a memorable first impression, but he grounded out to second base with the bases loaded to end the first inning, then grounded to shortstop with runners on second and third to end the third.
Down 2-0 at one point, the Giants scored single runs in the fifth and eighth innings to forge a 2-2 tie, then used Scutaro's walk-off walk to even the series at a game apiece.
Roger Kieschnick's third hit of the game, a one-out single, got the Giants' game-winning inning rolling. Scutaro came to the plate after Boston left-hander Franklin Morales (2-1) issued a two-out walk to pinch hitter Andres Torres, then hit pinch hitter Hector Sanchez to load the bases.
Villarreal, called up from Triple-A Pawtucket on Monday, failed to throw a strike with any of his four pitches to Scutaro, dropping the Red Sox into a first-place tie with the Tampa Bay Rays in the American League East.
Sergio Romo (4-6), the third Giants pitcher, got the win after pitching a 1-2-3 top of the ninth.
The ninth-inning excitement was set up when the Giants tied the game in the last of the eighth on Buster Posey's sacrifice fly off Red Sox reliever Junichi Tazawa. The long flyball, caught in foul territory by Boston right fielder Shane Victorino, scored Scutaro, who had singled.
Victorino earlier hit his eighth homer of the season, a solo shot that staked Red Sox starter Jake Peavy to a 2-0 lead in the third inning.
Neither starter factored in the decision.
Facing a San Francisco lineup that was without Pablo Sandoval, who was scratched shortly before game time because of a sore back, Peavy gave up extra-base hits in the fourth, fifth and sixth innings, yet still managed to hold the Giants to one run in 5 2/3 innings. He gave up five hits, walked one and struck out four.
Giants starter Ryan Vogelsong settled down after allowing two runs on five hits in the first three innings. In easily his best outing since breaking bones in and below his left pinkie finger on May 20, the veteran completed seven innings, striking out five and walking one. He gave up two runs on six hits.
Will Middlebrooks had two of Boston's seven hits.
Both teams failed to maximize their scoring opportunities early on.
The Red Sox built a 2-0 lead on Mike Carp's sacrifice fly in the first inning and Victorino's homer in the third. Vogelsong stranded the bases loaded in the first and runners on second and third in the third, keeping the Giants within arm's length.
The Giants got within 2-1 in the fifth on an RBI triple by Joaquin Arias. However, Peavy then got three consecutive groundballs, two with the infield in, to leave Arias anchored at third.
NOTES: The Red Sox have not announced when Dempster will rejoin the rotation. With off days upcoming Thursday and next Monday, the team could pitch its other four starters on regular rest until late next week. ... Rehabbing RHP Clay Buchholz threw a 46-pitch simulated game at AT&T Park on Tuesday and was given the green light to advance to a full bullpen session Friday in Los Angeles. The tentative plan is to have Buchholz make three minor league starts, the first of which could come as early as Sunday for short-season Class A Lowell. ... At 20 years and 323 days old, Bogaerts became the youngest player to debut for the Red Sox since RF Dwight Evans made his first appearance in 1972 at age 20 years and 318 days. ... Bogaerts wore No. 72. ... The Giants scratched RHP Chad Gaudin from his scheduled start in the series finale Wednesday, replacing him with LHP Barry Zito. Gaudin, who has experienced numbness in his right (pitching) hand in recent starts, was placed on the disabled list with what the Giants called carpal tunnel on his right side. ... The Giants created a second roster opening Tuesday by designating LF Jeff Francoeur for assignment. LHP Mike Kickham and RHP Jean Machi were promoted from Triple-A Fresno to join the team. ... The Giants announced before the game that CF Angel Pagan (hamstring) would start an injury-rehab stint at Triple-A Fresno on Friday. The goal is to activate him when rosters expand Sept. 1.