Bill Hall singled home the go-ahead run in the sixth with his first hit since joining the Giants four days ago and later doubled.
The Giants beat Arizona for the fifth straight time.
Willie Bloomquist and Chris Young hit solo home runs, ending Bumgarner’s 10-start string without allowing a homer. But that was about all the Diamondbacks could muster against the Giants’ 21-year-old lefty, who entered the game with the fifth-worst support in the majors (2.65 runs per game).
Bumgarner (3-8) gave up five hits and struck out six. Arizona had runners at first and second with two outs in the ninth, but Brian Wilson retired pinch-hitter Juan Miranda on a grounder for his 20th save in 22 chances.
Joe Saunders (3-7) allowed three runs and threw a season-high 115 pitches in seven innings for Arizona.
San Francisco scored two insurance runs off closer J.J. Putz in the ninth. Eli Whiteside tripled home Hall and scored on a wild pitch.
Aubrey Huff singled twice, drove in a run and scored for the Giants, who are 7-1 against Arizona this season with one to play in this three-game series.
In the Arizona eighth, Kelly Johnson tried to score what would have been the tying run from first on Young’s double down the left-field line, but was out easily at home on the relay throw from shortstop Miguel Tejada.
Huff singled with one out in the sixth, then Pat Burrell walked to set up Hall’s RBI hit. Moments later, Hall was called for interference going into second base, a ruling that resulted in an inning-ending double play.
The Giants scored in the first after a double play erased Aaron Rowand’s leadoff single. Pablo Sandoval singled, Cody Ross walked and Huff singled.
Bloomquist, hitless in his previous 12 at bats, hit Bumgarner’s 2-0 pitch just over the left-field wall for his second home run of the season to tie it at 1 in the third. It was the first home run the Giants’ lefty has allowed in 67 innings.
San Francisco quickly regained the lead 2-1 when Ross led off the fourth with a double and scored when Burrell tripled off the Arizona bullpen fence down the left-field line.
Young homer also barely cleared the left-field fence to tie it at 2 in the fourth.
NOTES: Bumgarner had not allowed a home run since a solo shot by Arizona’s Justin Upton’s at Chase Field on April 17. … After the enclosed structure was cooled by air conditioning, the Chase Field roof was opened just before the first pitch even though it was 106 degrees outside. … Arizona’s Xavier Nady struck out four times. … Bumgarner’s three victories all have come on the road. … All eight games between the Diamondbacks and Giants have been decided by three runs or fewer. … The Giants are 14-5 against left-handed starters.
(Copyright 2011 by CBS San Francisco. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. Wire services may have contributed to this report.)