SAN DIEGO - Yonder Alonso scored the winning run when San Francisco second baseman Marco Scutaro couldn't come up with former UA Wildcat Nick Hundley's grounder, lifting the San Diego Padres to an 8-7 victory in 12 innings over the Giants on Saturday night.

Alonso reached base with his third double of the game, went to third on Jedd Gyorko's single and scored on Scutaro's miscue.

Sergio Romo (1-2) took the loss, the Giants' fourth straight, and their third extra-inning defeat in four games.

Joe Thatcher (1-0) pitched the 12th inning giving up two hits for the win.

San Diego trailed 5-0 before rallying for six runs in the fourth inning.

Alonso and Chris Denorfia each had two-run doubles to chase Barry Zito.

Zito gave up six runs - five unearned in 3 2/3 innings.

He had four strikeouts and walked one.

Disappointment has been common for Zito in Petco Park. He hasn't made it through the fifth inning in five of his last seven starts in San Diego, and hasn't won there since Aug. 2, 2008.

Hunter Pence's two-run double in the fifth gave San Francisco a 7-6 advantage before the Padres tied it in the seventh inning on Kyle Blanks' single that scored Chase Headley.

Brandon Crawford hit a three-run homer in the second inning gave San Francisco a quick lead.

The Giants added two more in the third on an error by left fielder Carlos Quentin.

The second run scored on an RBI double by the Giants' Buster Posey.

Blaks went 3 for 6 in his first game back after injuring his eyelid crashing into the wall in San Francisco last week.

The outfielder pinch-hit on Friday.

Giants left-hander Jeremy Affeldt (right oblique strain) pitched a bullpen session Saturday.

The San Francisco reliever is eligible to come off the 15-day DL on Tuesday