(Sports Network) - Braden Looper has been a big reason behind the St. Louis Cardinals' turnaround this season. Tonight he goes for win No. 7 when the Cardinals start a three-game series with the Houston Astros at Busch Stadium.

After winning a World Series title in 2006, St. Louis struggled mightily a year ago on its way to a 78-84 finish, seven games back of the NL Central champion Chicago Cubs.

This season, though, the Cardinals are right in the thick of the division race at 30-22, sitting just a half-game behind the first-place Cubs.

Looper has been the ace for St. Louis and is 6-3 with a 4.34 earned run average. He picked up the win in his last start on Wednesday against the San Diego Padres, allowing three runs and eight hits in five innings.

The 33-year-old right-hander held the Astros scoreless over seven innings in a no-decision earlier in the year and is 7-3 lifetime against them with four saves and a 2.50 ERA in 36 games. He is 3-1 with a 2.89 ERA in six starts against Houston.

St. Louis, though, enters tonight's opener on a sour note after falling, 4-3, in 10 innings to the Los Angeles Dodgers on Sunday in the finale of a three- game set at Dodger Stadium.

Mike Parisi (0-1) served up Andre Ethier's game-winning RBI single, as the Cardinals lost for just the second time in their last seven tries. Albert Pujols went 2-for-5 with an RBI in the loss.

Houston, meanwhile, has been equally surprising this season and is just a game back of the Cards in the Central. However, the Astros also enter tonight's opener on a losing note after they were routed, 15-6, by the Philadelphia Phillies in the finale of a four-game set on Sunday

Chris Sampson allowed four runs on five hits in his five-inning start, but the Astros bullpen allowed 11 runs over four innings. Fernando Nieve (0-1) took the loss after a brutal appearance, surrendering four runs on four hits without recording an out.

Carlos Lee homered and drove in four, while Lance Berkman continued his torrid pace and went 2- for-5 with a run scored and an RBI, as the Astros lost for just the second time in their last six games.

Berkman, who ranks among baseball's leaders in batting average (.385), homers (16) and RBI (46), is hitting .488 with eight homers and 21 RBIs in May. In six games against the Cardinals this season the four-time All-Star is 7-for-21 with three homers and five RBI.

Heading to the hill for the 'Stros tonight will be Shawn Chacon, who will try to string back-to-back wins together after setting a major league record by failing to earn a decision in his first nine starts of a season.

Chacon finally earned a win on Wednesday against Chicago, as he limited the Cubs to three runs and five hits in seven innings, lowering his ERA on the season to 4.11.

Houston is 5-5 in Chacon's starts this year.

Chacon has yet to record a decision against the Cardinals in 12 games (five starts) against them, but has pitched to a 3.69 ERA in those outings.

The 30-year-old righty has also held slugger Albert Pujols in check over the course of his career. Pujols is just 3-for-16 lifetime against him, but has hit Houston pitching hard this season, going 8-for-20 against them with three homers and six RBI.

St. Louis has won four of six against the Astros this season and has won six of the last eight matchups in the series.