Cory Luebke surrendered just two runs over six innings and Nick Hundley added four hits as the Padres took a 5-3 decision over the Giants in the opener of a three-game set at AT&T Park.
Luebke (3-1) scattered seven hits while striking out three and Huston Street pitched a perfect bottom of the ninth to record his third save of the year.
"Anytime you throw that many pitches early you have to find a way to get as many innings as you can out of your arm," said Luebke. "I just wanted to try to get through six and turn it over to those guys (the bullpen) because they've been lights out for us."
Hundley finished with an RBI and a run scored while Chase Headley scored twice and also knocked in a run to help the Padres earn their second straight victory.
Eric Hacker (0-1) took the loss in his first major league start after yielding three runs on eight hits. Hacker did fan seven while his battery mate Buster Posey belted a solo home run and knocked in two of the Giants three runs.
Pablo Sandoval extended his franchise-record hitting streak to 20 games with a line-drive single in the bottom of the third inning but the Giants lost for the third time in four games.
"For you to have a good year, a winning year, you need the timely hits," remarked Giants manager Bruce Bochy. "We have talked about this in the past and you're hoping that doesn't get inside their head and they go up there with the confidence that they're going to get it done."
San Diego scored with two outs in the top of the first as Headley worked a walk and Hundley followed with a double to center field, scoring Headley for the 1-0 lead.
San Francisco answered quickly in the bottom half when Angel Pagan launched a leadoff homer into the seats in left field to tie the game at 1-1.
The Padres broke the tie in the fourth, scoring two runs on four consecutive singles as Hundley and Orlando Hudson each scored a run to give San Diego a 3-1 edge.
The Giants cut the margin in half with a run in the fifth as Melky Cabrera hit a ground-rule double to left and Posey scored him with a double to right two batters later.
Jesus Guzman hit a one-out double in the seventh, stole third, and scored on a single from Headley. After Hundley followed with a single, Headley scored on a wild pitch from Jeremy Affeldt to make it 5-2 San Diego.
Posey opened the bottom of the eighth inning with his fourth homer of the year to left-center field to account for the final margin.
Saturday's matchup features right-hander Tim Lincecum for the Giants against righty Anthony Bass of the Padres...The Giants went 1-for-9 with runners in scoring position and left eight on base...The Padres finished 3-for-8 with RISP while stranding seven.