By MATT BECKER
(AP) -- The NL West-leading San Francisco Giants have one of baseball's best rotations, but they haven't been pitching up to their lofty standards lately.
Madison Bumgarner is a part of this disturbing trend, and a start against the Arizona Diamondbacks might not help him out of his funk.
Bumgarner tries to avoid losing a third straight start and put an end to his struggles with the Diamondbacks in Wednesday night's finale in San Francisco.
Through last Tuesday, the Giants' starters had the majors' fifth-best ERA at 3.60, but in the last seven games the rotation has posted a 7.88 ERA. Despite the shaky starting pitching, San Francisco (77-59) still won five of those contests, and 11 of 15 overall.
The Giants were unable to overcome Ryan Vogelsong's poor performance Tuesday against Arizona, however.
Vogelsong, who had the league's best ERA three weeks ago, gave up six runs in 3 1-3 innings and San Francisco was forced to use 11 pitchers, matching a major league record for an extra-inning game. The Giants rallied - just like they have on several other occasions in the last week - behind Brandon Belt's two-run homer and Pablo Sandoval's two RBIs, but came up short in an 8-6, 11-inning defeat, snapping a three-game winning streak. They still remained 4 1/2 games ahead of second-place Los Angeles, which lost to San Diego.
"There's something special about this team that we kept fighting no matter what the situation," Belt said. "I can't say enough about what everybody in here is doing."
Arizona's Aaron Hill finished 5 for 5 and scored the go-ahead run on Jason Kubel's triple just out of right fielder Hunter Pence's reach. The Diamondbacks (67-70) ended a three-game losing streak and won for the third time in 12 games, but are still 10 1/2 back of the Giants.
Bumgarner (14-9, 3.07 ERA), the team leader in wins, has played a big part in San Francisco's rise to the top of the West, but he concluded August in disappointing fashion.
After giving up four runs over 6 1-3 innings in a 7-3 defeat to Atlanta on Aug. 25, Bumgarner allowed five runs in four innings in Friday's 6-4 loss to the Chicago Cubs. Prior to these duds, the left-hander had a 1.93 ERA over an eight-start stretch.
Friday's start was his shortest outing since also going four while allowing four runs in his season debut in a loss to Arizona. In his only other outing of the year against the Diamondbacks on May 11, Bumgarner gave up five runs in six innings of a 5-1 defeat.
One possible reason to be optimistic that things could be different Wednesday is his two starts with Arizona were both at Chase Field. In 12 games at AT&T Park, he is 8-2 with a 2.15 ERA, the NL's second-best home ERA.
Justin Upton hasn't enjoyed much success against the Giants, batting .189 with three RBIs and 23 strikeouts in his last 17 games in the series, but he's had Bumgarner's number, going 7 for 12 with a homer, double and three walks in their matchups.
Like Bumgarner, Arizona's Trevor Cahill (9-11, 4.02) has also struggled in this year's series, recording a 6.17 ERA in losing both outings. He was 3-0 with a 1.30 ERA in his previous four starts against the Giants.
Against the Dodgers on Friday, Cahill gave up three runs and four hits in 5 2-3 innings of a 4-3, 11-inning win. The right-hander has gone a season-high six consecutive starts without a victory.
Sandoval, who is 7 for 15 with four RBIs in his last four games, is 3 for 9 with a double lifetime against Cahill, but hasn't faced him this season.
Updated September 5, 2012