San Francisco showed off its deep bullpen on a day the Cubs had to look for yet another closer this season.
With Sergio Romo unavailable after pitching four of the last five days, the Giants turned to Santiago Casilla, who nailed down his first save of the season with two scoreless innings in a 3-2 victory over the Chicago Cubs on Saturday.
The Cubs threatened in the eighth, putting two on with no outs, before Soriano grounded out and Welington Castillo hit into a double play against Casilla.
"It's a nice luxury to have 2-3 guys, when you give your closer a break, that you're comfortable with them closing the game and they're comfortable out there," Giants manager Bruce Bochy said. "And what a great job Santiago did."
The Cubs put Kyuji Fujikawa on the 15-day disabled list with a strained right forearm. He had taken over for Carlos Marmol, who had been ineffective.
They could use a reliever like Casilla, who saved 25 games for the World Series champion Giants last season.
"He's versatile," Bochy said. "We can use him seventh, eighth and ninth inning, righties, lefties. He's throwing the ball well right now. He's got four pitches. He's a guy who likes being out there late in the ballgame too."
Madison Bumgarner allowed two runs while pitching neatly into the seventh inning and Marco Scutaro had three hits for the Giants.
Pinch-hitter Dioner Navarro hit a two-out, two-run homer off Bumgarner in the seventh to pull the Cubs to 3-2. It was Navarro's second career pinch home run in two days, each hit from a different side of the plate. His tying homer in the ninth Friday was hit from the left side.
"I'm just getting myself mentally ready, taking swings in the clubhouse," Navarro said. "Just go out there and swing.
Bumgarner (3-0) struck out six and walked two, one intentional, in 6 2-3 innings.
"All the pitches felt pretty good today," Bumgarner said.
Cubs starter Jeff Samardzija (1-2) allowed two runs and seven hits, struck out five and walked one in six innings. In his previous start, he struck out a career-high 13 and allowed four runs in 5 2-3 innings in Atlanta.
"You play a team like that, you've got to get ahead in the count," Samardzija said. "They work the count. They make you throw a lot of pitches."
A few snowflakes fell in the morning, and the temperature at first pitch was 38 degrees.
Gregor Blanco's RBI single snapped a scoreless tie in the fifth. He drove in Andres Torres, who led off with a double.
The Giants went ahead 2-0 in the sixth on Pablo Sandoval's RBI single. Scutaro scored after he led off with a single and advanced on a wild pitch. Samardzija struck out Andres Torres looking to end the inning.
Scutaro's RBI single off Michael Bowden in the seventh made it 3-0. Bumgarner scored from second as right fielder Scott Hairston threw to the middle of the infield.
The Cubs stranded seven on base, leaving the bases full in the second and two on in the sixth and eighth. Soriano had three hits for the Cubs.
"We're not quite clicking offensively, but the pitching is doing a good job," Bochy said. "When they stumble, the offense seems to pick it up when we need them."
Sandoval fell into the stands making a diving catch in the ninth. He had a bruised shin and said he should be ready to play Sunday.
NOTES: The Cubs called up reliever Rafael Dolis from Triple-A Iowa. Shawn Camp and James Russell are possible closers. Manager Dale Sveum said he won't use Marmol, who has a 12.27 ERA. Fujikawa (1-0, 12.46 ERA) said he felt discomfort in his forearm the last couple of days, but considers it a short-term injury. He said the injury has sidelined him for about 10 days in the past. . Cubs C Steve Clevenger was injured striking out to end the game. He will undergo an MRI for a possible oblique injury. . Giants CF Angel Pagan was scratched from Saturday's lineup because of a sore right wrist he jammed Thursday on a diving catch. He is day to day and entered as a defensive replacement in the eighth. He popped out in the ninth. ... Bochy presented Nate Schierholtz, now a Cubs OF, with his 2012 World Series ring during batting practice. Schierholtz hit .251 in 77 games with the Giants last season. . Cubs starting pitcher Scott Feldman has back tightness and will next pitch Saturday at Milwaukee, using the Cubs' off day Monday for extra rest. He was scheduled to start Wednesday against Texas. ... Cubs 2B Darwin Barney (knee laceration) was scheduled to begin his rehab assignment Saturday with Triple-A Iowa. He is expected to rejoin the Cubs on Tuesday against Texas. . Cubs 3B Ian Stewart (quadriceps) will begin his rehab assignment with Triple-A Iowa on Sunday.