Giants 2, Diamondbacks 0

Chad Gaudin might just be pitching himself right into a permanent spot in the San Francisco starting rotation.

He certainly pitched the defending World Series champion Giants to an important victory to begin the season's second half against the division-leading Arizona Diamondbacks, striking out eight in seven scoreless innings to build on his impressive monthlong stretch in a 2-0 win Friday night.

''It's huge,'' Gaudin said. ''Any win in our division is huge.''

All-Star Buster Posey hit an RBI double, Hunter Pence added a run-scoring single as 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.

''What a great job he did tonight, which we needed,'' manager Bruce Bochy said.

Gaudin is unbeaten in seven starts since joining the rotation in early June to replace the injured Ryan Vogelsong - and he is making for a tough decision by the Giants' brass when Vogelsong is ready to return next month.

''Obviously I'd like to start and enjoy starting,'' said Gaudin, so valuable for his versatility.

Not bad for a guy who signed a minor league deal with the Giants and had no guarantee of making the team out of spring training.

''I signed over here to do what I'm doing now,'' Gaudin said. ''It's great. I've put a lot of time and effort and work into having a good craft and pretty much dedicated myself to getting better and staying consistent. It's kind of surprising, but at the same time I kind of expect it out of myself.''

Gaudin's 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.

''Everything he does for us, it's a big lift,'' closer Sergio Romo said.

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.

''We had no offense going on at all tonight. They just shut us down,'' D-backs manager Kirk Gibson said.

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.

''You just try to be positive. Like, `Just get that out of the way,''' Kennedy said. ''Just keep going out there, grind away, find adjustments to do. That's what I really tried to do.''

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.