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HOUSTON -- Mark DeRosa hopes he's finally broken out the slump that's followed his wrist injury.

DeRosa homered twice at Minute Maid Park for the second time this season and the St. Louis Cardinals beat the Astros 7-3 on Monday night, a few hours after Houston fired manager Cecil Cooper.

DeRosa hurt his left wrist on June 30 and has said he'll need surgery after the season. He hadn't homered since Aug. 7 and drove in four runs for the first time since before the injury.

"A lot's been made of my wrist and I understand that," he said. "I've also felt terrible at the plate from a fundamental side. After I hurt myself, I tried to compensate and cheat and try different things. Finally, over the last two to three days, I've gotten in the cage and grinded it out."

DeRosa said it's just a coincidence that he had a breakout game in Houston, where he also hit two homers against the Astros in July.

"You have certain parks that you hit better at," DeRosa said. "I don't really think much about it."

DeRosa spoiled Dave Clark's major league managing debut for the Astros. Clark, Cooper's third-base coach, was named Houston's interim manager for the last two weeks of the regular season, but the Astros lost their eighth straight.

"I expected to win, but it's been a pretty hectic day," Clark said. "This is bittersweet, but I enjoyed what I was doing and I look forward to the last 12 days."

DeRosa also had a two-run double for the Cardinals, who reduced their magic number for winning the NL Central to three.

Kyle Lohse (6-8) allowed three runs and five hits in six innings to earn his first win since Aug. 10. Lohse has been coping with a nagging forearm injury and skipped his last turn in the rotation as a result.

He was encouraged after allowing three runs and five hits in six innings.

"I didn't really have any issues with it," Lohse said of the injury. "Mentally, I was locked in a lot better. I wasn't getting frustrated by not putting the ball where I wanted to. All-around, I felt a lot better."

Houston starter Wandy Rodriguez (13-11) had given up no more than one run in 11 of his previous 14 starts, but trailed 3-0 after the first inning in this one.

Albert Pujols doubled to right center with two outs and scored on Matt Holliday's single to left. Ryan Ludwick singled and DeRosa drove in two with a double off the right-field wall. Ludwick beat the throw home, but DeRosa was tagged out trying to stretch his hit to a triple.

Miguel Tejada homered off Lohse in the bottom of the first, his 12th.

Jason LaRue and Skip Schumaker led off the second with singles and LaRue scored on Julio Lugo's fly ball to right. Brendan Ryan beat out an infield single and Schumaker scored for a 5-1 lead.

DeRosa homered to left in the third off Rodriguez, who came in with a 1.58 ERA at home this season. The 30-year-old left-hander was missing with his breaking ball, the pitch that's carried him all season.

"Just a couple of mistakes," he said. "I didn't have control of my breaking ball. I missed a lot."

Lohse retired nine straight before Lance Berkman's one-out single in the fourth, but Carlos Lee grounded into a double play.

Geoff Blum doubled in the fifth and scored on Humberto Quintero's one-out single to left. Lohse struck out Houston's next two hitters to end another quick inning.

Chad Paronto relieved Rodriguez for the sixth and DeRosa led off with a homer to left.

DeRosa hit two homers at Minute Maid Park on July 21, one off Rodriguez, in an 11-6 Houston win. The third baseman has 10 homers since the Cardinals acquired him from Cleveland on June 27.

Berkman homered to left-center in the sixth, his 23rd of the season and fifth in the last 10 games.

The Cardinals' bullpen gave up only one hit over the last three innings.

Game notes

DeRosa has four multihomer games in his career. ... Rodriguez lost for the first time in his last six starts at home. ... Al Pedrique, the Astros' minor league field coordinator, replaced Clark as Houston's third-base coach. ... St. Louis IF Troy Glaus did not travel with the team to Houston. Glaus pulled an oblique muscle on a swing nine days ago.