After learning that their top offensive threat could be sidelined longer than initially reported, the Cubs will look for answers as they continue a three-game series against the Houston Astros at Minute Maid Park on Tuesday.Soriano injured his right hamstring while running the bases in Sunday's loss to the New York Mets. He was originally expected to miss two to four weeks with a hamstring strain, but the team said Monday that an MRI revealed a tear.Soriano -- the team leader with 18 home runs, 132 hits and 74 runs -- could return around Labor Day, Cubs manager Lou Piniella said."It's a loss," Piniella said. "We're going to have to step up. We have a very young club. We'll just see how they respond."Chicago (58-53) didn't respond well in its first game without Soriano, managing only five hits while striking out 13 times in a 2-1, 10-inning loss. For the second consecutive night, the Cubs failed to capitalize on a Milwaukee loss, remaining one game behind the Brewers for the NL Central lead."Yeah, we'd like to have Soriano, but we don't so you flip the page and move on," said reliever Michael Wuertz, who suffered the defeat. "You can't worry about it. We've got 25 guys and we have to go out there and do our job."The Cubs, who lost for the seventh time in eight extra-inning games this year, have batted .244 while losing four of their last five contests.Meanwhile, the Astros (49-63) avoided a third straight loss and improved to 7-8 in extra-inning games. Ty Wigginton scored the winning run on backup catcher Eric Munson's two-out single -- the Astros' seventh walk-off hit this year."Whenever you get your chance to play, you have to do what you can to help the team win," Munson told the Astros' official Web site.The Cubs have won five of six road games started by Sean Marshall (5-5, 3.86 ERA), who will take the mound Tuesday. The left-hander is 3-1 with a 2.60 ERA away from Wrigley Field.On Thursday, though, he was tagged for a season-high seven earned runs in 2 2-3 innings of a 10-6 home loss to Philadelphia. Marshall, who had scratched his eye the day before that outing, had a 2.31 ERA in his previous four starts."I don't know what his problem was. He was getting the ball up some," Piniella said. "I know he scratched his cornea last night sleeping. I'm not so sure that had anything to do with it, but it might have."Houston's Chris Burke is 5-for-7 with a homer against Marshall.Woody Williams (5-12, 5.37) will try to bounce back from one of his worst starts of the year. The right-hander gave up seven runs and 13 hits -- both season highs -- in five innings against Atlanta on Thursday, but the Astros rallied for a 12-11 victory in 14 innings. Williams also appeared in relief on Sunday, holding Florida hitless in the sixth inning of Houston's 6-5 loss.He is 3-9 with a 4.42 ERA in 18 career games -- 17 starts -- against the Cubs, including 0-1 with a 2.77 ERA in two starts against them this season.Chicago outfielder Cliff Floyd is batting .370 (10-for-27) with two homers against Williams, while third baseman Aramis Ramirez is 13-for-43 (.302) with two homers against him.