SAN FRANCISCO (AP) — Chad Gaudin struck out eight in seven scoreless innings to build on his impressive monthlong stretch, All-Star Buster Posey hit an RBI double, and the San Francisco Giants beat the first-place Arizona Diamondbacks 2-0 on Friday night.

Hunter Pence added a run-scoring single as defending World Series champion San Francisco started a key series to open the second half by pulling within 5 1/2 games of the D-backs in the NL West race.

Arizona starter Ian Kennedy (3-7) was denied career win No. 50 yet again in his eighth try.

In his past four starts, Gaudin (4-1) has a 0.77 ERA, two earned runs in 23 1-3 innings. He has an 11-inning scoreless streak.

Gaudin is unbeaten in seven starts since joining the rotation in early June to replace the injured Ryan Vogelsong.

His only loss came in relief during an extra-inning loss April 24 against Arizona at home.

Gaudin also got a defensive gem from Giants rookie Kensuke Tanaka. The converted infielder made a sliding catch near the foul line in left field, reaching back over his head after overrunning the play to rob Paul Goldschmidt leading off the fourth. Gaudin tipped his cap to the outfielder.

The Giants are determined to put some steady play together — and Gaudin’s stellar outing was a start. The club began a key stretch with 10 games at home in AT&T Park, including Tuesday’s doubleheader with the Reds in which Cincinnati is the home team in the opener to make up a July 4 rainout in Ohio.

Gaudin allowed three hits and didn’t walk a batter for the second time in his seven starts. Sergio Romo, the Giants’ fifth reliever, finished the five-hitter for his 22nd save and San Francisco’s 10th shutout. Arizona was blanked for just the second time after losing 3-0 to Atlanta on June 28.

Santiago Casilla escaped a bases-loaded jam in the eighth. Romo has a 29-game scoreless streak against the D-backs spanning 21 2/3 innings and dating to Sept. 6, 2010.

Kennedy lost his third straight during an eight-start winless streak in which he went 0-3 since beating the Cubs on June 1 in Chicago.

He even shaved his beard during the All-Star break to try to get on track.

The right-hander said he had a professional barber give him the trim Monday, his first in 26 months since his daughter, Nora, was born in late April 2011.

“I needed a change,” he said.

But Arizona lost its sixth straight second-half opener.

Notes: D-backs RHP Brandon McCarthy is scheduled to pitch a rehab start Sunday for Triple-A Reno and likely one more after that before being re-evaluated. He collapsed at a Phoenix restaurant last month with a seizure related to the head injury he sustained while pitching last September. ... Giants RHP Ryan Vogelsong, who had surgery May 21 a day after breaking two bones in the pinkie area of his pitching hand, will face live hitters for the first time Saturday and could begin a rehab assignment early next week probably beginning with Class A San Jose before going to Double-A Richmond during the team’s next road trip out East. ... San Francisco INF Joaquin Arias isn’t likely to come off the DL on Tuesday when eligible as he returns from an emergency appendectomy. ... Giants CF Angel Pagan has begun baseball activities and agility work in Arizona as he tries to work back before season’s end from left hamstring surgery. ... Giants Hall of Fame broadcaster Lon Simmons celebrated his 90th birthday and threw out the ceremonial first pitch to a standing ovation from the sellout crowd of 41,924. “It always has surprised me,” Simmons said of the support. ... All-Star fathers: Giants Jeff Francoeur and Sandy Rosario each welcomed baby girls during the break, Emma Francoeur on Monday in Atlanta and Saadet Rosario on Thursday in New Jersey.