Oswalt entered Saturday's game in St. Louis having won his last six starts, allowing only five runs. But he gave up a three-run homer to Larry Walker and four runs overall in a 4-2 loss to Jason Marquis and the Cardinals.
The loss continued the Astros' struggles at Busch Stadium. Dating back to Game 1 of last year's National League championship series, the Cardinals have beaten the Astros nine straight at home. St. Louis has won eight of 10 against Houston overall this year and 28 of 37 against the NL Central.
Houston had won seven of eight coming into this series. But the Astros have dropped the first two games to fall below .500 (44-45) and into third place in the NL Central, 13½ games back of St. Louis.
"Right before the All-Star break, we played really well and did a good job of getting guys on base," Morgan Ensberg said. "The last two games, we just have flat out been beat."
St. Louis manager Tony La Russa said his team is doing all the little things right.
"We play a team game for nine innings," he said. "It sounds kind of corny, but we keep doing it."
Even more ominous for the Central Division was the resurgence of Marquis.
Marquis (9-6) had been struggling for the past month. The win was his first in six starts dating to June 10. He allowed two runs on six hits and two walks.
"That might have been his most impressive game," La Russa said. "He pitched eight strong innings in this heat, and stamina-wise he probably could have pitched the ninth."
However, La Russa wanted to give that opportunity to Jason Isringhausen, who had blown the save the night before. This time, Isringhausen pitched a scoreless ninth for his 26th save in 29 chances. The save was his 127th for the Cardinals, tying him with Bruce Sutter for third on the Cardinals' all-time saves list.
"I'd say that factored into it," La Russa said of getting Isringhausen another save opportunity as soon as possible. "He's a professional, but he's also a human being, so we wanted to get him a chance. He deserved that chance as much as Jason Marquis deserved the win."
Marquis said that he was not focused on snapping his winless streak.
"I don't think like that," he said. "I just try to take it one game at a time. I had a couple of starts against Toronto and Cincinnati where I thought I struggled, but I thought I've pitched pretty well since then."
Marquis' sinker was working well and he was also putting the ball over plate.
"He threw strikes early in the count and we swung at a lot of marginal pitches early in the count," Houston manager Phil Garner said. "His ball was moving good. He got a lot of groundball outs."
Prior to Saturday, Oswalt (12-8) had not lost since dropping a 3-1 decision to the New York Mets on June 7.
But like the rest of his teammates, Oswalt has struggled at Busch Stadium. He gave up four runs and eight hits in six innings Saturday. On April 5, Oswalt allowed six runs and 11 hits.
Ensberg's two-run homer in the first inning gave the Astros an early 2-0 lead. The homer was his 25th, tying a career high set in 2003 and gave him a new career best for RBI (67).
Oswalt held the lead until the fifth, when Marquis led off with a ground-rule double over center fielder Willy Taveras' head. David Eckstein sacrificed him to third and Jim Edmonds drove him in with a single to right.
Albert Pujols followed with a single to right, sending Edmonds to third. Walker worked Oswalt to a full-count before hitting a breaking ball over the wall in right to make it 4-2.
Marquis settled down after the first inning, allowing just four hits over the next seven innings.
- Houston had won seven consecutive series coming into this three-game set.
- Marquis' double was his National League-leading 16th hit as a pitcher. He also has one pinch hit.
- Craig Biggio's third-inning double was hit No. 2,731 for his career, moving him past Barry Bonds and into 49th place on the all-time list. Next up are Tony Perez (2,732) and Goose Goslin (2,735).
- After collecting five hits all month, Mark Grudzielanek has five hits in the first two games of the series.
- Lance Berkman, who has reached base in 25 of his last 26 games, went 2-for-2 with two walks and a run scored.
- St. Louis starters have allowed three runs or less in the last nine games.