"Each game is big for us because of the division we're in and the two teams ahead of us," Arrieta said of the Cardinals and Pirates, who are 1-2 in the National League Central. "We know they're not slowing down and we don't intend to, either. What we have to do now is continue to make it difficult for the guys ahead of us, continue to show that we're going to put pressure on and not let up."
It was the Cubs' 10th win in their last 11 games, and they now have a 3 1/2-game lead over the Giants in the NL Wild Card standings. Arrieta posted his 10th straight quality start, scattering four hits over 7 2/3 innings.
Jake Peavy took the loss, giving up two runs over five innings, the longest outing by a Giants starter in the series. San Francisco's starters compiled a 7.94 ERA in the series, giving up 15 earned runs over 17 innings. The Giants have lost six of their last eight games, all on the road.
"We have a long way to go," Peavy said. "We're not going to panic, I can promise you that."
MOMENTS THAT MATTERED Start me up:Dexter Fowler set the tone in the first, battling Peavy in a 12-pitch at-bat. Fowler struck out, but Kyle Schwarber drew a walk after an eight-pitch at-bat and reached third one out later on Anthony Rizzo's single before scoring on Bryant's RBI single. Peavy needed 38 pitches to get through the inning. Bryant leads all Major League rookies with 65 RBIs.
"You have to give Peavy credit for hanging in there -- he was battling from the very first moment of the game," Cubs manager Joe Maddon said.
Scary stuff: Giants left fielder Nori Aoki was struck in the batting helmet above the right ear by an Arrieta pitch in the third inning and immediately left the game. Aoki was able to rise under his own power before head athletic trainer Dave Groeschner led him to the clubhouse. Afterward, Aoki said he felt fine and that Giants medical personnel will continue to monitor his condition through Monday's scheduled off-day.
"At first I felt a little nauseous," Aoki said. "But now I have just a little headache." More >
Hit machine: Arrieta hit his second career triple with one out in the second and then scored on Addison Russell's sacrifice fly. Arrieta also tripled last Sept. 24 against the Cardinals. He's the third pitcher to hit a triple this season, joining the Reds' Michael Lorenzen and the Padres' Tyson Ross.
"I was giving some of my teammates a hard time, telling them I have more pop than they do, and I can hit it through the wind," Arrieta said. "[Bryant] has all this pop and Rizzo and they're hitting fly balls to shallow right. It's not that hard. I go up there trying to get a pitch I can put good swings on. Thankfully, I was able to do that first pitch. I'm sure Peavy wasn't very excited. It ended up being a huge run for us."
Late-inning drama: The Giants, who went 0-fo-11 with runners in scoring position, launched serious scoring bids in the final two innings. In the eighth, they staged a two-out rally as Matt Duffy singled off Arrieta and Buster Posey singled off reliever Justin Grimm. Hunter Pence then drove Grimm's first pitch, a 96 mph fastball, to deep right-center field, where Fowler caught the ball a step or two in front of the ivy.
San Francisco loaded the bases with nobody out in the ninth before Cubs closer Hector Rondon struck out the next three batters. Pinch-hitter Hector Sanchez and Angel Pagan went down swinging before Gregor Blanco took a 3-2 pitch -- which the Giants believed was wide -- for strike three.
"We were one of those base hits, which we've gotten so many times this year, away from winning," Peavy said. More >
"It's big. It builds up a lot of confidence, which I think we've got already. We're playing a good team, man. They're the world champions. You've got to respect that. They kept grinding in the last inning [Saturday] and today. You can never give up on those guys. We're going to go back there [to San Francisco] and have to play the same way, play hard." -- Cubs catcher Miguel Montero on the sweep.
In the Chicago fourth, Montero was called out at first on a force play after hitting a grounder to shortstop Brandon Crawford. The Cubs challenged the call, and after a review, it was overturned and Montero was safe.
WHAT'S NEXT Giants: San Francisco will receive a much-needed scheduled off-day Monday before confronting the American League West-leading Houston Astros in a two-game series at AT&T Park. Tuesday's 7:15 p.m. PT series opener will feature a clash of talented left-handers, Madison Bumgarner of the Giants and Scott Kazmir of the Astros.
Cubs: After an off-day Monday, the Cubs play host to the Brewers for a three-game series, starting Tuesday. Dan Haren will make his second start since he was acquired by Chicago. In his debut against the Pirates, he gave up two home runs over five innings. First pitch is scheduled for 7:05 p.m. CT at Wrigley Field.