What is it with the Houston Astros after the all-star break? No team seems to surge post-break in recent years like the Astros, and it’s happening again.

Stuck in last place in the NL Central at 19-28 and nine games out of first at the end of May, Houston just swept St. Louis and is now a game behind the first-place Cardinals entering play Thursday. Houston is 30-18 since that low point on May 31. Also at the end of May, the Astros were only 9-15 at home, but they are 18-8 at Minute Maid Park since, the third-best winning percentage (.692) in the NL.

“We've been doing this since I got here," Houston pitcher Roy Oswalt said to reporters. "The first half is played to keep close, the second half is to gain ground and maybe catch up and go ahead by the end."

Wednesday’s 4-3 win over St. Louis showed how well things are going for Houston right now. The Cards led 3-2 entering the bottom of the ninth, and the Astros had been 2-40 when trailing after eight innings, while the Cardinals had been 48-1 when leading after eight.

So, of course, Houston rallied on a Miguel Tejada walk-off single. The two runs scored were the first runs allowed by Cards All-Star closer Ryan Franklin in 18 innings.

So how are the Astros doing this? Certainly pitching has been the biggest part. In the past 23 games, the team ERA is 3.26 with 18 quality starts. Wandy Rodriguez has become the team ace ahead of Oswalt. He allowed just a run in Tuesday’s win over the Cardinals, which ended an 18 1/3-inning scoreless streak for the left-hander. Rodriguez still won his 10th game and is seventh in the NL with a 2.72 ERA. Oswalt, meanwhile, has allowed three earned runs or less in his past six starts (2.00 ERA), and Houston has won five of those.

Another amazing factor in Houston’s surge is that it hasn’t done it courtesy of a long winning streak. The team’s season high is just a four-game streak, which it will be looking to tie Friday against the Mets.

In addition, Houston isn’t getting a lot lately out of first baseman Lance Berkman. He hasn’t started five of the past six games because of a left calf strain. Berkman has just one homer and eight RBI this month, but the Astros are 13-6. Carlos Lee and Miguel Tejada have picked up the slack when Berkman has been out or struggling, while Michael Bourn leads the NL with 36 steals this season.

After this weekend’s series with the Mets, we should really find out about Houston. It plays four games at the Cubs, three at St. Louis, three vs. the Giants and three vs. the Brewers. Those are all playoff-caliber clubs. The good news for those series against the Cubs and Cards is that the pitching is lined up to where both Oswalt and Rodriguez will each pitch in both series (neither pitches this weekend).

Before you go putting money on Houston at +700 on BetUS to win the NL Central, I would caution you to at least wait to see if the Astros can add pitching at the trade deadline. Sure, the rotation has been solid lately, but do you really trust Mike Hampton, Russ Ortiz and Brian Moehler as 60 percent of any rotation?

I sure don’t. The law of averages will catch up to Houston at some point without a major move.