Jonathan Sanchez had another wild day on the mound which has become typical of the San Francisco left-hander's season.
The Giants' offense was even worse, continuing another troubling trend for the defending World Series champs.
Sanchez was off with his command, walking three and throwing two wild pitches, and San Francisco stranded 10 baserunners in a 4-2 loss to the Oakland Athletics on Saturday night.
"We're in a rut right now," Giants manager Bruce Bochy said. "We've got some young kids trying to get settled in but there's just no excuse. We're better than this."
San Francisco dropped its third straight game overall and second consecutive to its cross-bay rivals.
In both losses to the A's, the Giants got men on base with little problem but failed to come through after that.
They left the bases loaded in the second inning against Oakland pitcher Guillermo Moscoso, stranded two in the fourth and two more in the sixth. Typical of San Francisco's night, Manny Burriss drew a one-out walk in the ninth but Pablo Sandoval grounded into a game-ending 6-4-3 double play.
"That's been the case the last few days," Bochy said. "We're having a hard time driving in runs. That's what it comes down to and that's what wins ballgames for you. We're getting them out there, we're just not getting a hit with runners in scoring position."
Aubrey Huff drove in a run for the Giants and Nate Schierholtz added two hits.
Brad Ziegler (2-0) struck out Cody Ross to end the fifth, the only batter he faced. Joey Devine, Brian Fuentes, Grant Balfour and Andrew Bailey each pitched a scoreless inning, with Bailey getting his fourth save in five chances.
Sanchez (4-5) pitched a season-low 4 2-3 innings, allowing four runs on six hits. He walked three and struck out three in falling to 1-3 over his last seven starts.
"I gave up a couple of high hits and they scored," said Sanchez, who has only one win in his last seven starts. "They knew I was throwing strikes and they were just looking down the middle and swinging."
Moscoso lasted 4 2-3 innings, giving up two unearned runs on three hits. He walked three and struck out one.
The Giants broke a scoreless tie in the fifth with the help of the A's defense. Chris Stewart was credited with a single after Scott Sizemore apparently caught his spikes in the dirt on a grounder and could not make an accurate throw.
Moscoso walked Andres Torres and then threw away Burriss' bunt away, allowing Stewart to score. One out later, Huff hit a sacrifice fly.
The A's came right back in their half of the fifth. Barton and Pennington had their run-scoring doubles and Coco Crisp walked ahead of Matsui's two-run single.
NOTES: Both teams used switch hitters in the top three spots of the batting order. ... Giants INF Mark DeRosa began hitting off a tee. ... Giants' OF Darren Ford is 2 for 11 with four strikeouts in his rehab. ... Huff is batting .308 in June after hitting only .218 through May 31.