A pair of All-Star pitchers failed in their bid to get the game series versus the Chicago Cubs at AT&T Park.
Tim Lincecum and Ryan Vogelsong both suffered defeats to the Cubs and the latter was dealt the loss in Tuesday's 5-2 decision. Vogelsong allowed three runs and seven hits in five innings of work to fall to 10-5 this season.
Jeff Keppinger was the only productive player at the plate, going 3-for-5 with a pair of RBI for the Giants, who have lost three straight and 21 of their past 30 contests to fall six games back of Arizona for the NL West lead.
"We're digging ourselves a big hole to get out of," Giants manager Bruce Bochy said.
The Giants are 3-5 on a 12-game homestand and will host the Diamondbacks for three games this upcoming weekend. They have gone just 10-14 at home since the All-Star break.
Meanwhile, Bumgarner has the honor of helping the defending World Series champions salvage the finale of this set and is 8-12 in 27 starts to go along with a 3.59 ERA this season. He is coming off Friday's 2-1 win over Houston in which he allowed only one run and five hits in 6 1/3 innings. The lefty had lost three of four decisions before defeating the Astros.
Bumgarner, who is 5-6 in 14 home starts this season, lost to the Cubs back on May 13 and is 1-1 with a 2.89 ERA in three career starts in this series.
Chicago won for the third time in its last 10 games and will wrap up a six- game road trip today before heading back to the Windy City for a six-game residency versus Pittsburgh and Cincinnati.
Matt Garza earned the win for the Cubs by allowing only two runs on nine hits over 6 2/3 innings. He also struck out six batters and added two hits at the plate before Sean Marshall, Kerry Wood and Carlos Marmol held the Giants off the board the rest of the way. Marmol posted his 31st save with a pair of K's in the ninth inning.
"People damaged our playoff hopes the first four months," Garza said on the club's site. "I'm fine with paying it back. If we're not in it, we might as well play spoilers. Playing spoilers isn't as fun but you might as well do it and make people mad at you."
Rodrigo Lopez will try to pitch the Cubs to a series sweep when he toes the rubber Wednesday. He is 4-5 with a 4.80 ERA in 21 games (11 starts) this season and has lost back-to-back trips to the mound, including Friday's 5-2 setback at Milwaukee. He gave up four runs -- two earned -- in six innings.
Lopez, a right-hander, lost to the Giants on June 28 and is 0-4 with a 6.31 ERA in seven career starts against them.
Chicago is 5-3 against the Giants this season.