SAN FRANCISCO (AP) -- Oakland starter Greg Smith didn't get rattled when San Francisco's Omar Vizquel stole home in the second inning. If anything, it seemed to calm the Athletics' erratic left-hander.
Smith (4-5) gave up three hits in five innings and overcame a season-high six walks to outpitch Zito in a matchup of struggling pitchers.
"I had checked [Vizquel] before but I had things on my mind," Smith said. "He picked the right time to go. I didn't hear a thing. For some reason, him not being on third relaxed me."
Zito (2-10) was attempting to win consecutive starts for the first time this season, but he allowed six hits and four runs in 5 2/3 innings. He walked four and struck out three.
Since leaving the A's and signing a $126 million, seven-year contract with the Giants before last season, the 2002 AL Cy Young Award winner is only 13-23. Zito is also winless in three starts against his former team.
"I can't sit around and pity myself and get depressed," said Zito, who has not won consecutive games since his final two starts in 2007. "I can't afford that luxury."
Mark Ellis went 2-for-4 with a double and scored twice while Jack Cust had two RBIs for Oakland. The A's have won four straight and six of seven against the Giants, matching their longest streak ever against their cross-Bay rivals.
Chad Gaudin, Keith Foulke and Huston Street completed the five-hitter for Oakland. Street pitched a perfect ninth, but his outing was briefly interrupted with two outs when the infield sprinklers came on during his windup and Fred Lewis at-bat.
Making his first interleague start, Smith struggled with his control throughout the game and walked three of the first 10 batters he faced. He also walked the bases loaded in the fifth but got out of that jam by getting Bengie Molina to fly out to right and striking out Aaron Rowand.
Smith also singled off Zito in the fifth in his first official at-bat in the majors. Smith had a sacrifice in the third.
"I felt like I was fighting myself, but a win is a win and I'll take it," Smith said. "I threw more balls than strikes and walked the bases loaded twice. I was inconsistent but bottom line is we won. I'll take that every time."
Vizquel's steal of home provided the lone highlight for San Francisco. It was the first steal of home by a Giants' player since Moises Alou against Arizona on Sept. 27, 2006, and the first straight steal of home by a San Francisco player since Max Venable on April 14, 1983.
"I'm glad it didn't make a difference in the game," Oakland manager Bob Geren said. "That's an unusual play. We were all yelling but he flat out couldn't hear."
Zito, San Francisco's struggling lefty, retired six of the first seven he faced but ran into problems in the third when Oakland scored three runs on three hits and a walk.
"It hurts to not help your team," Zito said. "But I've got to come back. I've got another test in five days."
Zito's troubles continued in the sixth when he gave up a pair of singles then issued back-to-back walks to force in a run. That was all for San Francisco manager Bruce Bochy, who called for reliever Vinnie Chulk as Zito jogged off the field to a chorus of boos from the Giants' crowd.
"We're in a rut right now and we know it, here at home," Bochy said. "We've played so well on the road, especially the last two road trips. We're just not pitching as well here. It's pretty simple. We know we're not hitting quite as well here [either]. Right now we have some guys that aren't quite locked in at the plate."
Oakland sent OF Travis Buck to Triple-A Sacramento to make room for Sweeney. ... Oakland DH Frank Thomas has been told by the A's to back off all baseball activities until July 1 while he recovers from right quadriceps tendinitis. ... Giants RHP Merkin Valdez, on the DL since May 15 with a strained right elbow, is scheduled to undergo additional tests on his throwing arm next week. ... The Giants wore throwback uniforms with bright orange jerseys the team sported in the 1980s.