After modest improvement over the past two months, the San Diego Padres have hit an ugly patch.

Matt Cain pitched eight dominating innings and the San Francisco Giants scored eight runs in the third inning to move into first place in the NL West with a 10-1 win over the Padres on Friday night.

San Diego lost its fourth consecutive game and has been outscored 28-2.

"We need a couple of good outings and some length from our starter," Padres manager Bud Black said. "The story of the game was the eight-run inning. When you have Cain against you, that's not a good combination."

Ross Ohlendorf (4-4) was not up to the challenge for the second straight start. The right-hander allowed a career-high eight runs on six hits in 2 1-3 innings.

In his last outing, he gave up seven runs in three innings of Sunday's 11-5 loss at Pittsburgh. Ohlendorf's ERA has risen from 5.45 to 7.58 after his last two starts.

"Getting behind in the count certainly didn't help," Ohlendorf said. "I didn't bury the guys when I needed to bury them."

The Padres, which had their four-game home winning streak snapped, were 32-27 record since June 12 before this latest losing streak.

Cain (12-5), who pitched a perfect game on June 13, surrendered one run on four hits. The right-hander didn't allow his first hit until Yonder Alonso's one-out double in the fifth. Alonso scored one out later on Everth Cabrera's single.

Cain, 6-0 in nine starts following a San Francisco loss, struck out six and did not walk a batter.

"He threw a lot of strikes," Padres rookie catcher Yasmani Grandal said. "He throws everything for strikes. He just keeps you off balance. He was real tough."

The Giants moved one-half game ahead of the Los Angeles Dodgers, who lost 4-3 in 11 innings at Atlanta.

Marco Scutaro homered and drove in two runs and Angel Pagan had three hits and two RBIs to lead the Giants' 15-hit attack. All nine San Francisco starters had at least one hit.

San Francisco played its second game since outfielder Melky Cabrera, was suspended on Wednesday for 50 games following a positive test for testosterone.

Scutaro hit a solo homer in the first inning before San Francisco's season-high scoring output in the third off and reliever Nick Mikolas.

The Giants eight runs came on eight hits including two doubles and a triple two walks and a passed ball as they sent 13 batters to the plate.

Pagan had an RBI triple and a run-scoring single in the inning. Scutaro, Pablo Sandoval, Gregor Blanco and Cain all had RBI singles and Hunter Spence drove in a run with a double.

Ohlendorf gave up a leadoff double in the inning before getting an out. He then allowed the next six batters to reach safely before getting pulled for Mikolas.

San Francisco has won 18 of the last 24 meetings with the Padres.

NOTES: In Ohlendorf's last start, Pittsburgh scored nine runs in the fourth inning, six off against Ohlendorf. . San Francisco has won 10 of its last 14 road games since the All-Star break, outscoring its opponents by a 103-45 margin. . The Giants recalled OF Justin Christian and RHP Eric Hacker from Triple-A Fresno on Friday. RHP Dan Otero was optioned to Fresno. . San Diego activated Grandal (strained right oblique) from the 15-day DL. C Nick Hundley (bruised right knee) was placed on the 15-day DL. . Giants LHP Barry Zito (9-8, 4.29 ERA) faces off against Padres LHP Eric Stults (3-2, 2.45) on Saturday night.