Right-hander Matt Cain faces Colorado for the 26th time in game series with the Rockies.
The Giants won their seventh straight game on Saturday, when Brett Pill hit a pair of triples, including a go-ahead two-run triple in the eighth in a 6-5 decision.
The win cut San Francisco's deficit in the National League West to five games in back of Arizona, which lost to San Diego on Saturday. The Giants trail Atlanta by five games in the NL wild card race.
Carlos Beltran went 3-for-5 with an RBI and a run scored.
Eric Surkamp started on the mound, but was pulled after 4 2/3 innings as he had walked six and given up a run on three hits with four strikeouts. Waldis Joaquin (1-0) earned the first win of his career for getting the final two outs of the seventh inning.
Santiago Casilla worked a shaky ninth inning for his fifth save of the season.
Drew Pomeranz gave up just two runs on four hits with two walks and five strikeouts over 5 2/3 innings. Huston Street (1-4) gave up four runs -- three earned -- while recording just one out in the eighth to take the loss.
Cain, a 26-year-old from Dothan, Ala., is 12-7 in 25 meetings with the Rockies, including a 3-1 win in their last meeting on June 3, in which he allowed a run on four hits in seven innings.
He's won seven of 13 decisions since, but is 0-1 in his last two starts, including a 3-1 loss at San Diego on Sept. 7.
His last outing was a no-decision, again against the Padres, in which he allowed a run and four hits in what ended as a 3-2 San Francisco victory.
The Giants are 17-14 in Cain's starts in 2011.
For Colorado, 26-year-old Esmil Rogers makes his sixth attempt at a first defeat of San Francisco.
The Dominican is 0-2 with a blown save in five previous meetings while allowing 19 earned runs on 22 hits in just 17 innings of work.
He faced the Giants for the one and only time this season on April 18 in Colorado and was chased after three innings after surrendering eight runs on six hits.
Rogers is 0-4 in his last six outings overall, last winning on Aug. 9 at Cincinnati.
San Francisco has won 10 of 14 versus Colorado this year and 14 of the last 19 meetings overall.