Wildness hampered left-hander Jonathan Sanchez, whose own command lacked compared with that of Ryan Dempster. Sanchez (1-2) walked six and hit a batter, and smallish Ryan Theriot muscled up and hit a two-run home run to lead the Cubs to their fourth straight victory.
Pablo Sandoval hit an RBI single for the Giants, who dropped the opener of a seven-game, three-city road trip. Trailing the Majors in offense, the Giants have scored four runs combined over the past three games.
Aaron Rowand, who went 0-for-4 with a pair of strikeouts, said Dempster was hitting the corners as he often does. Dempster (2-1) allowed two runs and five hits over seven innings. He walked two and struck out seven.
"He kept hitting the outside corner with his slider, so he gets you looking for the slider and then he pumps a couple of fastballs by you," Rowand said. "Through my career, chasing him, he does a real good job of keeping guys off balance."
Giants hitters, who collectively struck out 11 times, looked it.
Manager Bruce Bochy was matter-of-fact about his offense.
"We can't sit on one or two runs," Bochy said. "We've got to get this offense going. We just got shut down. Dempster threw a good ballgame.
"We got some guys that are cold right now, there's no getting around it. They'll come around, sooner rather than later. It's definitely going to take some pressure off these pitchers. The pitching's been fine. Our issue right now is trying to get some runs on the board."
Sanchez put pressure on himself by missing the plate often in a laborious, 30-pitch first inning. One pitch to Geovany Soto, a 3-2 splitter with the bases loaded and two outs, just missed to force in the Cubs' first run.
Sanchez said he thought he threw a strike, and if he gets that call from umpire Jerry Layne?
"Yeah, it's going to be a different [result]," Sanchez said. "I was going to throw less pitches and better pitches. When you have an inning like that, when you walk a couple of guys, you're going to get tired [sooner] and you're not going to make the same pitches later in the ballgame."
Sanchez might have felt some effects in the second when Theriot, who came in with nine homers in 1,360 career at-bats, ripped his third homer in four days to make it 3-0.
"I didn't know he was that hot," Sanchez said. "For a small guy, I thought he was going to [hit a] ground ball or fly ball. He doesn't hit a lot of home runs. I was comfortable pitching to him. It was a good pitch in, but it wasn't in-in. He was cheating on it and he got a fastball and got it."
So, do the Giants despair after getting down by a few runs?
"You don't want to think like that," Bochy said. "We got down 3-0 but that's the last thing we need to be thinking about."
The Cubs added a run in the fifth after Randy Winn lost Soto's fly ball in a bank of Wrigley's lights. Soto was credited with a hit, and Reed Johnson followed a batter later with a sacrifice fly.
"You don't see that too often from Randy," Bochy said. "He's a great outfielder."
Sandoval, who is batting .387 over his past 16 games, flied out in the eighth against Carlos Marmol as the potential tying runner. The Giants also started a mild threat in the ninth against closer Kevin Gregg, but pinch-hitter Rich Aurilia lined out to Johnson in center with a runner aboard to end the game.
Bochy said to expect a couple of changes in Tuesday's series finale, which ace Tim Lincecum starts for the Giants. Sandoval needs a day off and Aurilia will be in the lineup.
"I may change the order a little bit and see if we can get it going," Bochy said. "At this point you go with your gut."
And the Giants won't simply rely on Lincecum tossing a shutout.
"We know how good Timmy is -- everybody does," Bochy said. "But at the same time, we've got to get runs."