HOUSTON -- Ivan Rodriguez's number change to 77 from 12 on Monday didn't have anything to do with changing his or the Astros' luck on the field, but it could be representative of the change the Houston catcher has seen in the team's clubhouse over the past month.

Rodriguez, who will be behind the plate catching Astros ace Roy Oswalt in the series finale against the St. Louis Cardinals on Wednesday, said that he's seen a major difference in the team's pitching and play on the field recently. The improved performance has put Houston back in the hunt for the National League Central crown.

"The pitchers have done a far better job, and we're playing good defense and getting the offense going," Rodriguez said. "We're playing good right now, but we have to keep it going and not take anything for granted. We just have to go out there and stay positive and play hard every day."

In the past two months, Houston has focused on the game's finer points, and by doing so it has posted the second-best record in the NL, going 29-17 since May 30.

"[Astros general manager] Ed Wade told us before the All-Star break that we just have to do the little things in game to win ballgames," Rodriguez said. "Bunt the ball here, bunt the ball there to move a guy over and be smart on the bases. Things like that are what we're trying to do. We did that in Los Angeles and won two games there against the team with the best record. As long as we keep doing that, we're going to be in good shape."

The Astros' surge reminds the veteran catcher of the Florida Marlins team he played for in 2003, and he sees a lot of similarities to that team, which got off to a slow start but rallied in the second half to make the playoffs on its way to a World Series championship.

"I see something very special in this team," Rodriguez said. "In '03, I remember we had a bad first half and then we came back and finished 10 games over .500 and were able to go to the playoffs and eventually won the World Series. That's baseball. It doesn't matter if you're winning by 10 or losing by 10, you have to keep playing the game hard."

Having veterans such as Rodriguez, Mike Hampton, Russ Ortiz, Lance Berkman, Carlos Lee and Miguel Tejada, who all have been in tight division races before, is something that the Astros hope will benefit them down the stretch.

"I think a team is always good when you have veterans on your team and a few young guys," Michael Bourn said. "That way the veterans can help us and teach us and help us get comfortable. The more you're around them and the more you see them go, it picks you up and lets you get comfortable, and you feel more like you're part of a team and that's what we have now."

Pitching matchup
HOU: RHP Roy Oswalt (6-4, 3.65 ERA)
Oswalt has won three of his past four starts and three consecutive decisions. He's coming off a masterful four-hit complete-game win over the Los Angeles Dodgers on Friday, in which he struck out five batters. He's 3-0 with a 1.66 ERA in his past five starts. Oswalt faced the Cardinals on April 11 at Busch Stadium and allowed nine hits and six runs in his second start of the season. He's 9-7 with a 3.11 ERA in 26 regular-season appearances (25 starts) against St. Louis.

STL: RHP Chris Carpenter (8-3, 2.26 ERA)
Carpenter wasn't as sharp last time out as he has been in other starts this year, but he was just as effective. The St. Louis ace allowed seven hits in eight shutout innings on Friday night against the D-backs, striking out seven and using two double-play balls to escape jams. Carpenter kept the ball down and several of his hits just found holes on the infield, an encouraging sign for Carpenter and the Cardinals. He came within one inning of his 13th career shutout but was taken out after 103 pitches. There was no need for manager Tony La Russa and the Cardinals to push their ace any further with the recent arm troubles he has had and with the Cardinals having a comfortable 4-0 lead at the time.

Tidbits
Pitcher Jeremy Johnson had his contract purchased from the Astros by the LG Twins in Korea on Tuesday. The right-hander posted a 5-8 record with a 3.51 ERA in 21 games, including 13 starts, for Triple-A Round Rock this season. Johnson was originally signed by Houston as a Minor League free agent on Dec. 30, 2008.

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Up next
• Thursday: Off-day
• Friday: Astros (Mike Hampton, 5-7, 4.63) vs. Mets (Johan Santana, 11-7, 2.92), 7:05 p.m. CT
• Saturday: Astros (Russ Ortiz, 3-4, 4.33) vs. Mets (TBD), 6:05 p.m. CT