Giants 2, Rockies 1: Madison Bumgarner won his 15th game and Hunter Pence drove in the tiebreaking run as host San Francisco lowered its magic number to win the National League West to eight.

Brandon Crawford tripled and doubled and red-hot Buster Posey had two hits for the Giants, who increased their lead over the second-place Los Angeles Dodgers to eight games. Bumgarner (15-10), who was 0-3 in his last four starts, allowed one run, four hits, walked a career-high five and struck out six in six innings to improve to 3-0 against the Rockies in 2012.

Rookie Josh Rutledge had an RBI triple for the Rockies, who have lost 10 of their last 12 overall and on the road. Colorado's Jhoulys Chacin allowed five hits and one run in five innings. He also helped himself when he doubled with one out in the fifth and scored on Rutledge's two-out shot in the right-center field gap to tie the game.

Crawford led off third inning with a triple off the top of the center field wall and with one out scored on Wilin Rosario's passed ball. The Giants strung together three straight singles to start the sixth inning, with Pence capping the outburst with a grounder through the right side to score Pablo Sandoval and make a loser out of Guillermo Moscosco (3-2).

Sergio Romo, the fifth reliever, struck out pinch hitter Jason Giambi to earn his 12th save in 13 chances as San Francisco, which opened a 10-game homestand before its 156th consecutive sellout, improved to 11-4 against Colorado this season.

GAME NOTEBOOK: Rockies LF Carlos Gonzalez did not start and grounded out as a pinch hitter with one out in the ninth inning. He left Sunday's 12-11 loss at San Diego after the top of the sixth with left hamstring tightness. ... Giants LF Gregor Blanco did not play because of a sore left shoulder and will likely miss the series. ... Posey is 17-for-36 (.472) in his last nine games.