SAN FRANCISCO -- The Arizona Diamondbacks pitching staff began its three-game series against the San Francisco Giants on a historic run at AT&T Park.

Then Rubby De La Rosa and four of his mates went out and improved upon it Friday night.

De La Rosa and four relievers combined on a two-hit shutout, lifting the Diamondbacks to a 2-0 victory that further crippled the Giants' playoff hopes.

The win was the Diamondbacks' fifth in a row at AT&T Park and their 10th of the season against the Giants, the first time they've reached double figures in wins over San Francisco since 2008.

More impressive, the shutout lowered the Diamondbacks' ERA to 1.46 in eight games in San Francisco this season. No team has ever finished a season (minimum of six games) with an ERA under 2.20 at AT&T Park.

"It's a good pitchers' park, especially at night," noted Diamondbacks manager Chip Hale. "You make a mistake here, there's a chance it's going to stay in the ballpark. Whereas in Phoenix, it doesn't."

With the loss, the Giants (77-70) fell 8 1/2 games behind the Los Angeles Dodgers (85-61) in the National League West with just 15 games to go.

The Dodgers beat the Pittsburgh Pirates 6-2 on Friday night.

"It's an uphill climb," Giants manager Bruce Bochy assured. "You never know. I don't think we can lose another game, to be honest.

"As long as you're still alive, you've got to believe."

Coming off his shortest outing of the season, during which he was bombed for six runs on nine hits in two innings by the Dodgers, De La Rosa held the Giants to one hit -- a fourth-inning single by third baseman Matt Duffy -- before leaving a 2-0 game with the bases loaded and two outs in the sixth.

"You have to forget about it," he said of his disastrous outing last Saturday. "He (Bumgarner) is a good pitcher. I just wanted to give my team a chance. Keep the score tight."

Left-hander Andrew Chafin came on to get Giants first baseman Brandon Belt to ground out to end the sixth inning, preserving the shutout.

Right-handers Randall Delgado, Daniel Hudson and closer Brad Ziegler finished up with one inning apiece, retiring nine of the 10 batters they faced.

The only baserunner against a Diamondbacks reliever came on Giants catcher Buster Posey's one-out single off Ziegler in the ninth.

But Ziegler struck out reserve first baseman Nick Noonan and right fielder Marlon Byrd to close it out and register his 27th save.

De La Rosa (13-8) walked four and struck out five.

"He did a great job," Hale said of De La Rosa. "He gave us all he had for as long as he could do it."

The Diamondbacks scored both their runs off Giants ace left-hander Madison Bumgarner in the sixth inning, aided by a San Francisco error.

Center fielder A.J. Pollock led off the inning with a single, his second hit of the game, and raced home when first baseman Paul Goldschmidt lined a double down the left-field line that got under the glove of Giants left fielder Alejandro De Aza for an error.

Goldschmidt wound up at third, from where he dashed home on catcher Welington Castillo's grounder to shortstop.

Pollock and Goldschmidt had two hits apiece for the Diamondbacks, who failed to hit a home run for just the second time in their last 11 games.

The closest the Giants came to scoring came in the eighth, when Pollock reached over the fence in center field to rob pinch-hitter Jarrett Parker of a home run leading off the inning.

"It was fun. I've never done it before," Pollock said of the catch. "I've been on the other end."

Bumgarner (18-8) was denied a 19th win despite allowing just two runs on five hits in eight innings. He walked three and struck out seven.

"We lost. That's not ideal," a thoroughly disappointed Bumgarner said after his first home loss since June 12. "We can't afford any (more) losses."

The Giants had won eight of their previous 11 games, scoring 67 runs during that stretch.

NOTES: The record for best ERA in a season at AT&T Park is 2.20, held by the 2014 Los Angeles Dodgers. ... Including games at Candlestick Park, the Giants' previous home, the record is 1.15, set by the Chicago Cubs in 1985. ... Diamondbacks starters are 5-0 with a 0.82 ERA during the eight-game run at AT&T. ... Giants LHP Madison Bumgarner threw a season-high 117 pitches in his eight innings. ... Giants 1B Brandon Belt left the game in the top of the ninth inning because of a headache. ... Giants RHP Tim Hudson threw a 20-pitch bullpen session before Friday's game and declared himself fine to pitch the series finale Sunday. Hudson had to leave his last start in the fifth inning with pain in his right hip.