Nothing seemed to go Doug Davis' way in this one.
Davis (1-7) allowed 10 earned runs and 12 hits over 4 1-3 innings, the most runs he has given up since his major league debut on Aug. 9, 1999.
"They're a pitchable team," Davis said of the Giants. "I think there's holes in everybody's swing if you're able to execute. It was just one of those days. I feel like every time they hit the ball, it was where we weren't, whether it was hard or soft.
"Obviously, we don't play anyone over the fence for the home runs."
Pat Burrell and Aaron Rowand each drove in three runs as the Giants surpassed their season high of 12 runs, which they set at St. Louis on June 2. They also stretched their winning streak to six games.
Burrell, who came in just 1 for 15 lifetime against Davis, had three hits against the lefty. He scored two runs and homered. Rowand had two hits, scored twice and hit a three-run double.
"Just a tough day for Doug," Cubs manager Mike Quade said. "We scored enough runs, we did enough offense. We just didn't get a good start from him."
Before the game, Quade stressed the importance of getting as much out of his starters as possible on this seven-day, eight-game homestand. The Cubs won't get another day off until the All-Star break.
They forfeited their off day Monday to make up a game against the Colorado Rockies and added a fourth game to this series due to a May 15 rainout.
"We're trying like a son of a gun to make sure we don't abuse them and use them too much," Quade said. "We've done our best to avoid that and we'll continue to do that."
To help the bullpen, the Cubs recalled right-hander Marcos Mateo and optioned DJ LeMahieu to Triple-A Iowa after the game.
Ryan Vogelsong (6-1) got the win despite allowing a season-high six runs — three earned — and matched his high for the season with four walks in five innings.
San Francisco jumped on Davis early, starting with Rowand's walk to lead off the game and Miguel Tejada's single. Rowand scored on Aubrey Huff's soft single to right-center, diving into the plate to barely beat the throw by Cubs center fielder Tony Campana.
Cody Ross singled to load the bases as the first four Giants reached base. Davis recovered to get Pablo Sandoval to roll into a double play, which scored Tejada. Burrell tacked on a run with a two-out single.
Vogelsong, who entered with a 1.86 ERA, hadn't allowed more than two runs since he gave up five against the Mets on May 3 — a span of nine starts. The Cubs topped that in the second inning.
After Aramis Ramirez led off with a single, Pena homered into the right-field bleachers, pulling the Cubs within 3-2. It was Pena's eighth homer in his last 12 games and 17th since May 3.
With two outs in the second, Hill snuck an 0-1 pitch from Vogelsong just inside the right-field foul pole, tying the game. It was Hill's second homer of the season and first since April 28. It was also the Cubs' sixth homer in their last two games.
Huff worked out a walk to start the third, then scored on Sandoval's double that just eluded Cubs right fielder Kosuke Fukudome. Burrell followed with his seventh homer, a shot to left that gave San Francisco a 6-3 lead.
The Giants broke the game open and chased Davis with a five-run fifth, highlighted by a bases-clearing double by Rowand off Carpenter. Huff and Chris Stewart also drove in runs in the inning.
"The way the ball was carrying out there, I wasn't surprised to see a lot of runs scored," Giants manager Bruce Bochy said. "It was good to break out because we really needed it today."
Chicago came back with three unearned runs against Vogelsong in the fifth, a rally that included three walks, an error on second baseman Bill Hall and a bad-hop single by DeWitt that eluded Hall and drove in two runs, trimming the Giants' advantage to 11-6.
Vogelsong was removed for pinch-hitter Nate Schierholtz in the top of the sixth. Schierholtz then had an RBI single. Tejada capped the Giants' scoring with a solo homer in the ninth, his second of the season and first since April 8.
NOTES: Quade got a nice pregame surprise when it was announced that Bochy had added him to the NL staff for the All-Star game, to be played July 12 in Phoenix. Quade replaced former Washington manager Jim Riggleman, who resigned last week. ... The game was the first of a day-night doubleheader at Wrigley Field. The afternoon portion was a makeup of a game rained out on May 15. The Cubs, who also played a makeup game against Colorado on Monday, played their third team in three days. ... Cubs CF Marlon Byrd was hit by a pitch in his first rehab game for Triple-A Iowa. Byrd has been out since May 21 with facial fractures suffered when he was beaned by Boston's Alfredo Aceves. The Cubs are hoping that Byrd, who walked, stole a base and scored two runs in five plate appearances for Iowa, will return to the lineup next week.