"That was big for us tonight," manager Cecil Cooper said. "Probably the biggest one this year."
After spending seven innings scratching out two meaningless hits off Looper, the bats came to life in the ninth, and, within minutes, the Astros reversed a 2-0 deficit.
Darin Erstad knocked a one-out base hit to left field off Isringhausen, and he scored when Miguel Tejada sent a triple to the gap in right-center. After unsuccessfully trying to convince home-plate umpire Adrian Johnson that Isringhausen grazed him with a pitch, Lance Berkman lifted a fly ball to left that was deep enough to drive in the tying run.
Carlos Lee wasted no time during his at-bat, taking the first offering from Isringhausen and sending it to the seats in left-center.
The game ended after midnight CT thanks to a two-hour rain delay, but Astros players showed no sign of fatigue as they rehashed their come-from-behind win over their most fierce division rival.
"When you get a performance like that from your pitcher, there's nothing you can do," Lee said of Looper. "He pitched pretty much close to perfect -- never left the ball over the plate, always hitting the corners. He was on tonight. I guess we got lucky he didn't go the distance."
The luck set in when they faced Isringhausen, who took the loss for the second time in three outings.
"I was trying to somewhat pitch around Berkman, not give him anything good to hit, but I left a fastball enough to where he could get the bat on it," Isringhausen said. "And then, with Lee, it was just a pitch over the middle of the plate. Location.
"I kept a pitch away from Miguel and I thought he might roll over, but he stayed on it real well. What are you going to do? And then it was a terrible pitch to Lee. He's done the same thing before to me."
Berkman, who has three hits in 16 career at-bats against Isringhausen, said the St. Louis closer didn't look any different to him.
"He's always tough on me," Berkman said. "I hate facing that guy. He's very good. I know his velocity's down from the past, because he used to be able to throw like 96 [mph]. Heck, maybe he can still throw 96. I don't know. It seems like he goes to the cutter a lot more than he used to. For me, he's probably as tough as any pitcher in the league on me, so I have a tremendous respect for him."
The comeback win erased what would have been an undeserved loss for Shawn Chacon. The right-hander wasn't his sharpest on Friday, but he pitched well enough to win. This has been a recurring theme all month for the right-hander, who held the Cardinals to two runs over seven innings and walked away with a no-decision. He has produced five quality starts, but is winless in '08.
The Cardinals produced eight baserunners in the first two innings, but Chacon managed to keep the damage to a minimum.
"The first inning, I think he just couldn't settle in, couldn't get comfortable," Cooper said. "It looked like he was really kind of scuffling. The ball was running all over the place. He showed me a lot tonight. He stranded seven or eight guys. He really battled. He kept us in it."
Chacon admitted he didn't feel comfortable in the early innings and that he didn't loosen up until at least the third.
"I'm just happy with the way it turned out," he said. "The first inning, you might have thought the game might have been real ugly. For us to come back in the ninth and score three off of Isringhausen was awesome. That just goes to show you that, if you keep the game close as a starter, this team has the potential to score in bunches and to do it in one inning, too."
Reaching the .500 mark for the first time when a season is only 24-games-old might not seem like a big accomplishment, but the meaning was not lost on the Astros.
"We're playing better as a team, we're getting big hits and good pitching," Cooper said. "I guess I can say we're still playing good defense. We're just trying to have a good road trip. I thought if we could win five, six games on the trip it would be great for us."
"It means a lot," Lee said of the .500 mark. "It means we get to start over again."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.