CINCINNATI -- Scott Rolen joked that his first homer since July 6 was a career saver. It's no exaggeration to call it a game saver.

Rolen led off the seventh inning with a homer that ended Barry Zito's shutout, and the Cincinnati Reds rallied for a 4-2 victory Wednesday night, extending the San Francisco Giants' misery at Great American Ball Park.

The 37-year-old third baseman was batting .169 when he homered on a full-count pitch, ending a power drought brought on by his shoulder injury that needed surgery last season. Finally, Rolen -- in the last year of his contract -- could round the bases.

"[Shortstop Zack] Cozart was saying that it's a career saver," Rolen said. "That's kind of been the joke here. That's what happens when you get one hit every two weeks."

A career saver?

"Well, it wasn't quite that," manager Dusty Baker said. "When you're not swinging the bat well, life's miserable. He's hit some balls hard."

The Giants couldn't stop the Reds after Rolen's breakthrough homer, setting up another rough game at Great American. San Francisco has dropped seven straight and 12 of 16 at the ballpark. Zito remains winless there in six starts.

"I just didn't make that pitch to Rolen," Zito said. "That changed the whole inning. It shows you how quick this game can spiral."

Clay Hensley (1-2) threw wildly for an error after slipping as he fielded a bunt. Jeremy Affeldt's wild pitch allowed the go-ahead run to score.

Jose Arredondo (2-0) had one perfect inning. Sean Marshall pitched the ninth and remained perfect in four save chances.

The Reds have won five of their last six overall.

Before the game, the Giants put Aubrey Huff on the 15-day disabled list while he gets treatment for an anxiety attack. Huff left the team after having a tough time in a game on Saturday. He could rejoin the team in San Francisco next weekend.

Pablo Sandoval singled in the third inning, giving him a hit in each of the first 18 games. That matches Johnny Rucker's mark with the 1945 New York Giants for best season-opening streak in franchise history.

Neither team did much through the first six innings, when a steady rain forced the grounds crew to spread bags of drying material around the infield at each changeover.

Angel Pagan hit a solo homer in the third off Bronson Arroyo, giving him a 10-game hitting streak that matches his career high. Arroyo lasted five innings, giving up at least one hit in each of them. He allowed nine in all and one walk, but escaped with only two runs -- one earned.

"It's never fun to pitch in that kind of weather," Arroyo said. "It's definitely uncomfortable, plus they have a lot of left-handers, which makes it hard on me."

The Giants went only 1 for 6 with runners in scoring position, a recent theme. They're batting .156 with runners on second or third base in the last 10 games.

Until Wednesday night, Zito has struggled at Great American, going 0-2 in five starts with 7.20 ERA. The left-hander allowed only four singles through six shutout innings, then left after giving up Rolen's leadoff homer in the seventh on a full-count pitch that was over the plate.

Hensley, who hadn't allowed an earned run this season, gave up a single by Ryan Ludwick and set up the Reds' go-ahead runs with a slip. He momentarily lost his footing while fielding Ryan Hanigan's bunt, then threw wildly to first.

"It's kind of pretty much all on me," Hensley said. "In a situation like that, I need to reset my feet and get the out at first."

Drew Stubbs' walk loaded the bases, and Wilson Valdez's sacrifice fly tied it. Affeldt threw a wild pitch that let in another run, and Joey Votto doubled for a 4-2 lead.

Notes

The Reds swept a three-game series from the Giants at Great American last July. ... Ryan Vogelsong starts the final game of the series for SF. He's 2-3 career against the Reds with a 5.40 ERA. ... Homer Bailey starts for the Reds, looking for his second straight win. He went a season-high seven innings in a 9-4 win in Chicago on Friday. ... The Giants filled Huff's spot by calling up infielder Joaquin Arias from Triple-A Fresno, where he batted .400. ... Sandoval hit in 22 straight games last season, a career best. ... Sandoval hit a foul ball that cleared the stadium roof on the first base side.