Hunter Pence hit a grand slam to lead the Astros to a 4-2 win over the Cubs on Tuesday night to break a four-game losing streak against the division rival.
"It was definitely an important game," Lance Berkman said. "We can't afford to let them go up two. We've got a chance tomorrow to win the series instead of looking at just trying to salvage a game. So as far as May games go this one's important. Also for down the road, we need to know that we can win games like this."
A day after snapping a career-high 16-game hitting streak with an 0-for-4 night, Pence had three hits, including a shot to the first row in right field in the fourth inning. It landed near a neon orange sign that read "Hunter Pence Rocks" in bold block letters.
Astros manager Cecil Cooper had complained about the crowd being pro-Chicago on Monday. On Tuesday the Astros fans were much more vocal, especially during the fourth inning.
"They were loud, they got into it," Astros starter Chris Sampson said. "It gave us an extra shot of adrenaline. I know it did me. After Pence hit that grand slam I just wanted to go out and throw up some zeros and get after it."
Pence also had a single and a double and has 18 RBI in the last 18 games.
"When he's hitting like that he's pretty good," Cooper said.
Miguel Tejada doubled in the fourth inning for his 1,800th hit. He is the 44th shortstop in major league history to reach the milestone and has the most RBI (34) and hits (64) of any player at his position this season.
Berkman walked before Carlos Lee popped out. Geoff Blum then walked to load the bases before Pence's second career grand slam.
Astros closer Jose Valverde pitched a scoreless ninth for his 13th save in 16 opportunities.
Aramis Ramirez's two-run homer to left-center field put Chicago up 2-0 in the fourth inning. It was his second consecutive game with a home run after going 20 games without one. Derrek Lee doubled before the homer by Ramirez.
Sampson (3-3) continued his success against the Cubs, allowing seven hits and two runs in 6 2/3 innings. Sampson is 3-0 in four career starts against Chicago with four earned runs allowed.
"He was just real, real efficient with his pitches," Cooper said. "He was very crisp."
Sampson gave up a pair of singles with two outs in the first before retiring the next seven batters. After the home run by Ramirez in the fourth, he retired nine of the next 10.
He was replaced in the seventh inning by Doug Brocail after giving up a pair of singles and a walk.
Ryan Dempster (5-2) allowed six hits and four runs with five strikeouts in six innings.
"It was everything leading up to the home run that bothered me. It was just bad inning management," Dempster said of the fourth inning. "I had (Carlos) Lee at 0-2 and I had an opportunity to make a pitch and I didn't do it. One big hit killed me. I felt so good and I felt better as I went along. This was a game I felt I could have won."
Jose Ascanio, called up from Triple-A Iowa after Monday night's game, allowed two hits and walked two in two scoreless innings.
Kosuke Fukudome saved the Cubs from another homer with an impressive leaping catch at the right-field wall on a ball hit by Geoff Blum in the eighth inning.