Giants right fielder Hunter Pence hits his three-run home run.

Giants right fielder Hunter Pence (8) runs past a sign on the third base line that reads "I *heart* Hunter" after he hit his three-run home run.

A thin crowd watches from the Crawford Boxes during the first inning.

Giants starting pitcher Barry Zito pitches during the first inning.

Astros starting pitcher Dallas Keuchel pitches during the first inning.

Giants starting pitcher Barry Zito pitches during the first inning.

Giants starting pitcher Barry Zito pitches during the first inning.

Astros catcher Chris Snyder (18) beats the tag at home by San Francisco Giants catcher Buster Posey (28) on an RBI double by Astros center fielder Brandon Barnes.

Astros catcher Chris Snyder (18) beats the tag at home by Giants catcher Buster Posey (28) on an RBI double by Astros center fielder Brandon Barnes.

Astros catcher Chris Snyder (18) beats the tag at home by Giants catcher Buster Posey (28) on an RBI double by Astros center fielder Brandon Barnes.

Astros first baseman Brett Wallace (29) hits an RBI single during the third inning.

Giants starting pitcher Barry Zito (75) waits for Giants manager Bruce Bochy (15) to walk out to the mound to relieve him.

Astros center fielder Brandon Barnes (39) reacts as he strikes out.

Astros center fielder Brandon Barnes (39) reacts as he strikes out.

Giants 3, Astros 2 Astros right fielder Jimmy Paredes scores on a wild pitch as Giants starting pitcher Matt Cain dives for the throw to break open a 1-1 tie during the eighth inning.

Astros second baseman Jose Altuve reacts after popping out to end the game.

Giants third baseman Pablo Sandoval misplays a foul ball off the bat of Astros catcher Jason Castro during the first inning.

Sandoval knocked the ball high in the air and Giants shortstop Brandon Crawford raced in to scoop the ball off the turf for the third out.

Giants third baseman Pablo Sandoval, left, watches as shortstop Brandon Crawford races toward a misplayed a foul ball off the bat of Astros catcher Jason Castro.

Giants shortstop Brandon Crawford dives to catch a misplayed a foul ball off the bat of Astros catcher Jason Castro during the first inning.

Giants center fielder Angel Pagan tries to play a ball off the wall on a double by Astros first baseman Brett Wallace fourth inning.

Astros right fielder Jimmy Paredes takes off with a steal of second base during the first inning.

Giants center fielder Angel Pagan celebrates after hitting a home run off of Astros starting pitcher Bud Norris during the fifth inning.

Giants first baseman Brandon Belt scores past Astros catcher Jason Castro to tie the game at 2-2 during the ninth inning.

Astros starting pitcher Bud Norris pitches to Giants third baseman Pablo Sandoval during the first inning.

Astros shortstop Jimmy Paredes scores on a wild pitch as Giants starting pitcher Matt Cain reaches for the throw during the eighth inning.

Astros relief pitcher Wilton Lopez reacts as he is pulled from the game after two runs scored during the ninth inning.

Astros manager Tony DeFrancesco waits for a verdict from the umpires after contesting a triple by Giants center fielder Angel Pagan.

Giants starting pitcher Matt Cain reacts as Astros outfielder Fernando Martinez rounds the bases after hitting a home run during the fifth inning.

Astros outfielder Fernando Martinez celebrates with teammates after hitting a home run off of Giants starting pitcher Matt Cain during the fifth inning.

Astros starting pitcher Bud Norris wipes his face after leaving the game in the seventh inning.

Astros relief pitcher Wilton Lopez looks away after Giants first baseman Brandon Belt (9) scored to tie the game during the ninth inning.

Astros third baseman Marwin Gonzalez catches a foul ball off the bat of Giants center fielder Angel Pagan during the ninth inning.

Astros right fielder Jimmy Paredes stands for the national anthem before facing the San Francisco Giants.

Astros right fielder Jimmy Paredes gets a pat on the head from starting pitcher Bud Norris before facing the San Francisco Giants.