(Sports Network) - Dan Haren will try to pitch himself and the Arizona Diamondbacks back into the win column this afternoon, when they take on the San Francisco Giants in the finale of a three-game series at AT&T Park.

The Diamondbacks have lost five straight games and dropped to 2 1/2 games behind the Los Angeles Dodgers for the top spot in the National League West division, a position they once held comfortably. They have also lost nine in a row on the road.

Haren, meanwhile, has lost two straight starts and is winless in his last three outings. He lasted a season-low four innings in a 7-0 loss to the Dodgers the last time out on Friday, allowing five runs and six hits to fall to 14-8 with a 3.41 earned run average this season. He will face San Francisco for the third time this season and has split both matchups so far. In 11 career appearances, 10 of which have been starts, against the Giants, the right-hander is 5-4 with a 3.42 ERA.

Arizona, which is 0-5 on a six-game road trip, suffered a 5-4 loss on Tuesday night. Chris Snyder's two-run homer off Brian Wilson tied the game in the top of the ninth inning, but Pablo Sandoval slid home safely following a Eugenio Velez single to right field with one out in the home half for the win.

D'Backs starter Doug Davis allowed two runs in 5 1/3 innings, while Jon Rauch absorbed the loss for giving up the game-winning run. Rauch allowed Sandoval to reach base on a single before he came around to end the game.

The Giants have won four straight and five of six games. In last night's late- inning victory over the rival Diamondbacks, starter Barry Zito struck out nine batters and allowed five hits and two runs over six innings in the no- decision. Wilson was credited with the victory in the ninth despite allowing Snyder's game-tying two-run homer.

Making his first start since the 2006 season, Giants hurler Brad Hennessey gets the nod on Wednesday. Hennessey is 1-1 with a 12.46 earned run average in 13 relief outings this season, and last pitched on Sunday in an 11-6 win over the Pittsburgh Pirates. He didn't so well, yielding a run and two hits in just one-third of an inning.

Hennessey, recalled from Triple-A last Monday, replaces starter Kevin Correia, who has lost three of his last four decisions and owns a 7.84 ERA in his last two starts. Hennessey, whose last start was September 15, 2006 at St. Louis, has made a pair of relief appearances versus the D'Backs this season. He is 0-2 with a 4.72 ERA in 13 career games (three starts) against them.

The Diamondbacks are 7-6 against the Giants this season, with a 5-3 mark by the Bay.