Cain ended a 10-start winless stretch dating to last season, taking advantage of an early lead that held up in the Giants' 4-0 victory against the slumping Colorado Rockies on Monday night.
It was his first victory since beating the Rockies last Aug. 28.
"That's the least of my worries," Cain said. "I wanted to get us out of the nasty streak we got in against Cincinnati the last couple of days."
French-born Bruce Bochy moved past former San Francisco skipper Felipe Alou for most victories by a foreign-born manager in major league history with 1,034.
Aaron Rowand doubled and drove in two runs, including when he and Rich Aurilia each drew bases-loaded walks to force home a pair of insurance runs in the fifth. Rowand hit an RBI single in the first and Ray Durham also singled in a run that inning.
Cain (1-2) pitched four-hit ball and walked five over 5 1/3 innings, ending a five-start winless stretch to start the year. Vinnie Chulk, Tyler Walker and Brian Wilson finished the eight-hit shutout. Wilson struck out two, then allowed back-to-back hits in the ninth before getting Todd Helton on a called third strike to end it.
"No question it's great to get him a win," Bochy said. "He had good stuff. He didn't have his best command but he got it done. He's had some tough luck. ... It's nice for these starters to get wins. They work hard out there. For him, this is big. It's been a long time."
The Giants bounced back from losing a weekend series at home to Cincinnati, earning their fourth shutout. The Rockies were blanked for the third time.
Colorado manager Clint Hurdle was ejected in the first inning for arguing a balk call -- and wound up missing a two-minute delay for a neighborhood power outage in the bottom of the seventh.
Hurdle was yelling at plate umpire Paul Emmel from the dugout when Emmel tossed him, then Hurdle hustled to the field and spent several more minutes arguing with the umpire before finally heading for the tunnel to the clubhouse. It was Hurdle's first ejection of 2008.
"Obviously, Franklin's been called balking to first base before," Hurdle said. "I feel like he's under some scrutiny. I just felt it was a poor call. (The umpire) didn't think so. You know you can't argue a balk call but I didn't leave the dugout. I turned my back to walk away from it and he threw me out."
Durham followed Burriss with an RBI single, and Rowand singled in a run two batters later to stake Cain to a quick 2-0 cushion.
The Rockies, the defending National League champions, have lost eight of nine and their 1-8 record since April 20 is the worst in the majors. They are 1-4 in Morales' starts this year.
Morales walked three to load the bases in the fifth, leaving after putting Bengie Molina on base with the third free pass. Kip Wells relieved, gave up two walks and threw nine pitches before he was done.
"The wheels came off in the fifth," Hurdle said. "There's some flashes of some good things and there's still some inconsistencies."
Cain -- who went 7-16 last season despite consistently pitching well -- allowed four hits, struck out three and matched his season high with five walks. He has allowed two or fewer earned runs in 10 of his 12 career outings against Colorado, and owns a 6-3 record against the Rockies. He faced them in his major league debut on Aug. 29, 2005.
Colorado's Garrett Atkins extended his hitting streak to 13 games with a sixth-inning double.
Randy Winn and Durham pulled off a double steal in the fifth, and Eugenio Velez stole his sixth bag of the year in the eighth. The Giants had four steals on the night and have 30 stolen bases in the opening month for the most in San Francisco history, topping the 1999 team that had 28 in the initial month.
- Before the game, the Giants demoted $126 million left-hander Barry Zito to the bullpen to work out his problems as a reliever. Zito, the 2002 AL Cy Young Award winner with Oakland, has lost his first six starts this season and has a 7.53 ERA that jumped considerably after Zito was tagged for eight earned runs in a 10-1 loss Sunday to Cincinnati.
- The Rockies have now played in every NL West stadium this season.
- Morales, who has given up seven runs in first innings this season, matched his career high with five walks.