The Houston Astros could be on their way to a 100-loss season, but they're giving San Francisco fits this weekend.

The Astros will try to win five in a row for the first time since last August 22-26 when they go for a sweep of the playoff-contending Giants this afternoon at Minute Maid Park.

The Giants have lost 16 of their last 22 games, including a 7-5 defeat last night. Despite the struggles, the Giants remained 2 1/2 games behind Arizona for first place in the NL West.

Now the Giants will have to face a player they traded away a month ago.

Houston righty Henry Sosa takes a third stab at his first major league victory. Sosa will be facing his former team, as he was acquired from San Francisco on July 19 along with Double-A pitcher Jason Stoffel in exchange for infielder Jeff Keppinger.

Sosa has pitched six innings in each of his previous starts, losing most recently to the Chicago Cubs on Monday.

Even though this is Sosa's third major league, game he's waited a real long time for his first victory. He has pitched in parts of eight minor league seasons since being signed by the Giants as a non-drafted free agent out of the Dominican Republic. After joining the Astros organization, Sosa went 2-0 with a 2.89 ERA in three starts at Double-A Corpus Christi before being promoted to Triple-A Oklahoma City.

San Francisco lefty Dan Runzler will make his first major league start. Runzler, who has made 19 appearances this season and 71 over his career, He will start in place of Jonathan Sanchez, who is out with a sore left ankle.

Runzler made 10 starts for Triple-A Fresno. In 14 games overall for the team, he went 2-3 with a 4.17 ERA.

J.D. Martinez hit a two-run home run and two-run double as the Astros took a 7-5 win last night.

Jose Altuve went 3-for-5 with an inside-the-park home run, his first career round-tripper, for the Astros, who tied their season-high with their fourth straight win. Jordan Lyles (2-7) got the win as he gave up just two unearned runs on seven hits with two walks and four strikeouts over five innings.

"He pitched around seven hits and those runs were unearned," said Astros manager Brad Mills about Lyles. "The kid did a good job out there and the bullpen picked it up when we needed them to. It was a nice win to see out there tonight."

Houston now has a chance for just its second sweep of the season and first since a three-game sweep of the Cubs from May 30-June 1.

Cody Ross and Pablo Sandoval each drove in two runs for the Giants, who continue their free-fall with their fifth loss in their past six games. Madison Bumgarner (7-12) gave up seven runs -- six earned -- on 11 hits in 6 2/3 innings.

"He was a little off tonight," said Giants manager Bruce Bochy. "He made some mistakes and had some bad luck to go with it."

Houston was 2-7 vs. the Giants last season, losing the first seven contests before winning the final two.