DENVER -- Chad Bettis will have to continue waiting for his first major league victory.
The Colorado Rockies rookie pitched six innings in his sixth major league start but gave up two first-inning home runs as the San Francisco Giants beat the Rockies 5-3 on Tuesday night.
Bettis' record fell to 0-3 after he gave up nine hits and four runs, raising his ERA to 4.80.
Journeyman Yusmeiro Petit, taking injured Matt Cain's turn in the San Francisco rotation, allowed two runs in six innings and won for the first time as a starter since Aug. 27, 2009, against the Giants while pitching for the Arizona Diamondbacks.
In addition to back-to-back, two-out homers in the first inning by Hunter Pence and Pablo Sandoval, Bettis gave up a run in the sixth on Hector Sanchez's one-out single.
Bettis has allowed five homers in 30 innings. Pence's homer came after a single by Brandon Belt, who went 4-for-4.
The Rockies scored single runs in the second and third off Petit, who in 38 starts in the big leagues is 10-17 with a 5.15 ERA.
The Giants, who are 16-22 since the All-Star break, increased their lead to 5-2 with a run in the seventh off Adam Ottavino. Gregor Blanco led off with a double and took third when center fielder Charlie Blackmon picked up the ball and dropped it. Marco Scutaro brought Blanco home with a sacrifice fly.
The Rockies got the run back in the bottom of the inning against Sandy Rosario. He walked pinch-hitter Jordan Pacheco and yielded a double to Corey Dickerson. Pacheco scored on a groundout that moved Dickerson to third. But Rosario stranded him by getting Troy Tulowitzki to fly to short center and Michael Cuddyer to ground out.
Sergio Romo retired the side in order in the ninth to pick up his 32nd save in 36 chances.
Bettis retired the first two batters he faced in the first inning before Belt singled and Pence followed with a two-run homer. The next batter, Sandoval, homered to give the Giants a 3-0 lead.
Pence's home run landed on the concourse in left field. According to ESPN Stats and Information, the ball traveled 476 feet and is the longest homer in the majors this season.
In the third, Blackmon doubled home a run and then was sacrificed to third by Bettis. But Petit struck out Dickerson and got DJ LeMahieu on a flyout to end the inning.
Petit gave up two hits and two walks but just one run in the fourth. Wilin Rosario grounded a run-scoring single to right with one out. But with runners on first and second, Nolan Arenado flied out to short center field, Blackmon walked to load the bases and Bettis struck out.
NOTES: Giants OF Andres Torres will undergo surgery on Wednesday to have bone spurs removed from his left heel. Rehabilitation time is about six months, so Torres might not be ready at the start of the 2014 season. ... The back-to-back homers in the first inning by Pence and Sandoval were the first for the Giants since Sept. 20, 2012, when Sandoval and Buster Posey did it at AT&T Park against the Rockies. ... Rockies C Yorvit Torrealba was activated from the seven-day concussion disabled list and IF Ryan Wheeler was optioned to Triple-A Colorado Springs. Torrealba suffered his concussion on Aug. 18 when he was struck on the mask with a foul ball. ... Rockies LF Carlos Gonzalez (right middle finger sprain) took batting practice for the first time since he went on the 15-day disabled list retroactive to Aug. 5. ... Tulowitzki returned to the lineup after missing two games with soreness in his left side. But CF Dexter Fowler was not in the lineup. He was still sore after he bruised his left knee sliding into second base in the first inning on Monday and left the game in the second. ... Rockies RHP Roy Oswalt (left hamstring strain), who last pitched for the Rockies on July 7, threw 53 pitches in four innings in his second simulated game and then did some fielding drills afterward.