After rallying to win the series opener, the NL West-leading Giants look for a fifth consecutive victory over the lowly Astros on Wednesday night.San Francisco (72-57) had won five in a row before losing the final two of a four-game home series versus Atlanta last weekend. The Giants did not have an easy time in Houston on Tuesday, but backup catcher Hector Sanchez delivered a go-ahead RBI single to highlight a two-run ninth inning in a 3-2 victory at Minute Maid Park.Sanchez, 5 for 13 as a pinch-hitter this season, drove home Joaquin Arias after the infielder's pinch-hit double tied the game."The bench came through for us," San Francisco manager Bruce Bochy said. "They saved us. It just goes to show you how important the bench is. They delivered."The Giants have won four in a row against the Astros (40-89), including the last three by the same 3-2 margin.Angel Pagan homered for San Francisco, which increased its division lead to 3 1/2 games over a Los Angeles Dodgers club that has lost three straight. Pagan is 11 for 21 in his last five road games, and batting .441 with three home runs and 21 runs in his last 14 away from home.He's 6 for 16 in his last four games against the Astros, who will try to avoid a sixth consecutive home defeat.Barry Zito (10-8, 4.31 ERA) takes the mound for San Francisco looking to build on his performance against Atlanta on Thursday, when he allowed two runs and five hits in eight innings of a 5-2 win."It feels good to help the team," said Zito, who's 3-0 with a 3.94 ERA in his last five road starts.Zito has not helped his club by posting a 10.00 ERA while losing his last two starts versus Houston. The left-hander gave up five runs on two homers and walked three in five innings of a 6-3 home loss to the Astros on June 14.Facing the Giants for the first time, Houston starter Dallas Keuchel (1-6, 5.40) is 0-6 with a 6.61 ERA in nine starts since beating Cleveland in his second major league outing June 23. The left-hander allowed six runs in four innings of a 13-5 loss at St. Louis on Thursday."Mistakes are going to be made by young pitchers and young players," interim Astros manager Tony DeFrancesco said.Brett Wallace had three hits in the opener for the Astros, who have scored 15 runs while going 1-7 since DeFrancesco replaced the fired Brad Mills."Eventually, it is going to turn," DeFrancesco said. "We have a lot of confidence in the guys in there. The effort is there. I am watching guys go hard every day. It's sort of frustrating to the manager and coaching staff not to get the `W."Wallace is hitting .386 (17 for 44) at home this season.