Arizona (72-76) has reached the postseason four times in its 11-year history, and had a run last year before enduring a four-game sweep against Colorado in the NL championship series.

It's still possible to secure another berth this year, but the Diamondbacks must first halt their recent troubles. They are 4-15 since Aug. 24, when they owned a three-game lead over the second-place Los Angeles Dodgers in the NL West.

The Dodgers now have a 4 1/2-game advantage in the division.The Diamondbacks won't see the Dodgers again during the regular season, but the clubs could meet in Los Angeles if their records are tied at the end.

"We're not concerned about the Dodgers," Arizona's Tony Clark said. "We're concerned about ourselves."

Arizona will try to end its run of seven straight series losses after dropping two of three to Cincinnati over the weekend - capped by a pair of back-to-back 10-inning defeats, including Sunday's 2-1 decision.

Justin Upton went 4-for-5 with a homer for the Diamondbacks, who outhit the Reds 10-3. Arizona stranded 17 runners and went 0-for-13 with runners in scoring position to finish 2-for-35 in those situations during the series.

"Really frustrating," Diamondbacks manager Bob Melvin said. "It just seems like we put more and more pressure on ourselves, the more guys we get on there and the more the game goes along."

Arizona has lost eight of nine overall, including three straight at San Francisco (68-81) last week. The teams have split 14 matchups this season - five of which were decided by a run - but the Giants hold a 3-2 edge at Chase Field.

The Giants are third in the NL West - 4 1/2 games behind Arizona - but they've been playing like contenders lately by going 9-2 after a five-game losing streak from Aug. 29-Sept. 2.

San Francisco lost the opener of a four-game series at San Diego on Thursday, but bounced back to take the final three games including an 8-6, 10-inning victory on Sunday, when the team erased a four-run deficit.

Six relievers combined for 6 1-3 scoreless innings, and rookie catcher Pablo Sandoval scored the go-ahead run on a wild pitch for the Giants, who are 3-1 on their 11-game road trip.

Brad Hennessey (1-1, 9.64 ERA) gets the ball on Monday for San Francisco to face a familiar opponent. On Wednesday, the right-hander held the Diamondbacks to a run and four hits over six innings, but didn't factor in the a 4-3 home victory as he started for the first time since Sept. 15, 2006.

Hennessey is 0-2 with a 4.13 ERA while starting four of 14 career appearances versus Arizona, which counters with Doug Davis (6-8, 4.53), who gave up two runs and six hits over 5 1-3 innings, and didn't earn a decision in Tuesday's 5-4 loss at San Francisco.

The left-hander is 3-5 with a 4.98 ERA in 13 all-time games against the Giants.