Chase Headley hit a solo home run and Will Venable added a two-run double for the Padres, who had dropped three of four coming into Wednesday's action. Jason Marquis (4-5) won his third straight start as he gave up three runs -- one earned -- on three hits with a walk and eight strikeouts over 7 1/3 innings.
Ryan Theriot and Melky Cabrera each drove in a run for the Giants, who had won four of five prior to Wednesday's setback. Tim Lincecum (4-11) was handed the loss for giving up five runs on seven hits along with three walks and eight strikeouts over just 4 2/3 innings.
Headley gave the Padres the lead in the first with a solo homer in the first, but the Giants got it back in the bottom of the inning when Gregor Blanco singled, stole second, moved to third on a sac bunt and came home on Cabrera's sac fly.
San Diego went on top for good in the fourth as Guzman singled and Everth Cabrera walked. After Jason Marquis struck out for the second out of the inning, Venable smacked a double to left-center to score both runners for a 3-1 lead.
Guzman's two-run shot in the fifth made it a four-run game and he added his solo shot to start the eighth for a 6-1 lead.
A wild pitch from Marquis and RBI single by Theriot in the eighth got the Giants within three, but Huston Street, who got the final out of the eighth with runners on the corners, worked around a two-out double from Brandon Belt in the ninth to pick up his 17th save of the season.
Despite the loss, the Giants have still won six of nine against the Padres this season...The Giants host the Dodgers for three games starting on Friday...The Padres play three games in Miami beginning on Friday...Marquis improved to 6-5 in 15 games (14 starts) against the Giants...Lincecum fell to 10-5 in 21 starts against the Padres.
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