AP Baseball Writer
SAN FRANCISCO (AP) -- Carlos Gonzalez struck out swinging to end two innings and start another.
When Madison Bumgarner threw a curveball that hours later he wanted back, Gonzalez sent it over the right-field wall, onto the pathway and splashing into McCovey Cove on the bounce.
Other than that, the Colorado Rockies were stung by missed chances in a 4-2 loss to Bumgarner and the San Francisco Giants on Monday night, ending their five-game winning streak.
"He was throwing a lot of good pitches," Gonzalez said. "I think that was the one mistake he threw and I hit it out."
Hunter Pence hit a three-run homer deep into the seats in left-center in the first inning and Buster Posey added a late RBI single for the Giants.
Bumgarner (2-0) beat the Rockies for the sixth straight time and owns a seven-start unbeaten run in the rivalry. The left-hander began his career 0-3 against Colorado in five starts.
He struck out five and walked five in 5 2-3 innings Monday, allowing two runs and five hits.
One of those was Gonzalez's long homer to right in the third.
San Francisco extended its winning streak against the Rockies to seven games and bounced back from a 14-3 loss to St. Louis a day earlier when ace Matt Cain was tagged for nine runs in the fourth inning.
Michael Cuddyer had two hits and stole his first base for a Rockies team that had won five in a row since losing its opener 5-4 in 10 innings at Milwaukee. Dexter Fowler had his six-game hitting streak to start the season snapped as he went 0 for 4 with two strikeouts.
Pence sent the first pitch he saw from Jorge De La Rosa (0-1) deep into the bleachers in left-center for one of the hardest, longest balls he has hit at home since joining the Giants last July. Pablo Sandoval singled twice and scored a run.
"He's got some of the most power I've ever seen," Posey said of Pence. "I get to hit with him in BP every day, and I try to make sure I hit before him so I don't have to follow up his moonshots."
The reigning World Series champions returned to a more normal routine after three straight days of celebrations -- the flag raising Friday for the home opener, Posey's NL MVP presentation Saturday and then Sunday's ring ceremony.
Bumgarner pitched a 1-2-3 first, then issued at least one walk in each of the next four innings. After Cuddyer drew a leadoff walk in the fourth, Bumgarner was helped by a double play to get out of it unscathed. He walked Yorvit Torrealba to start the fifth, then Eric Young Jr. one out later before Bumgarner escaped another jam.
He is off to a solid start after struggling last postseason. Bumgarner, who spent the winter working on his mechanics, is trying to build on a 2012 season in which he won a career-best 16 games and had a 2.33 ERA in 14 home outings.
The curveball to Gonzalez was one of those he didn't have the "conviction" behind, as he put it.
"It would be hard to hit it any better," Bumgarner said.
Cuddyer hit a one-out single in the sixth and Chris Nelson had an RBI single two batters later. Giants manager Bruce Bochy called for Santiago Casilla as Bumgarner walked off to a standing ovation.
Casilla went 1 1-3 perfect innings, Jeremy Affeldt pitched a clean eighth and Sergio Romo allowed Josh Rutledge's leadoff double before striking out the side for his fourth save as the Giants retired 10 of the final 11 Rockies batters.
Posey's two-out single in the eighth provided some insurance.
De La Rosa allowed six hits and his only runs on Pence's homer, struck out three and walked one in a 76-pitch outing over six innings. He is 0-4 in his last seven starts dating to 2012.
Colorado starters reached 109 straight games without throwing 100 pitches, the longest such streak since pitch count data began in 1988.
The Giants went 14-4 against the Rockies last season for their most wins in the series, including 7-2 at AT&T Park.
First-year Rockies manager Walt Weiss returned to the Bay Area, where his big league career began as a first-round draft pick by Oakland in 1985. He spent the initial six of his 14 major league seasons with the Athletics.
"Welcome back, Walt!" one fan hollered as the skipper emerged for batting practice. He smiled and waved.