CHICAGO (AP) -- Now that Alfonso Soriano is back from the disabled list and feeling fine, the hits are coming at a healthy rate.
The Cubs won for the ninth time in 11 games and improved the NL's best record to 69-46.
It was an emphatic finish for the Cubs to a wild three-game series that saw Houston take the opener 2-0 after the game was called in the eighth inning because of violent storms. Chicago rallied for an 11-7 win Tuesday after blowing a five-run lead.
DeRosa's fourth career grand slam put Chicago ahead 5-4. Soriano capped the rally with his second three-run shot in as many days.
Soriano has 20 hits, including six homers, and 14 RBIs in 11 games since returning from a broken finger.
"It is a little surprising," Soriano said.
But not shocking. He is known to go on binges like this, after all.
His impact goes beyond the big hits, the dramatic drives. Manager Lou Piniella sees it every time he fills out his lineup card, which was why he kept insisting during a recent rough stretch that the offense would wake up once Soriano returned.
The Cubs have outscored opponents 75-39 over the past 11 games after managing two or less in four of the previous six.
"His presence in the lineup means a lot to us in different ways," Piniella said. "We can rest our catcher [Geovany Soto] a little more. We can rotate our outfield a little more. ... It gives us a lot of flexibility, and when he gets hot, it carries us."
DeRosa sees the trickle-down effect, although he wasn't about to attribute the struggles to Soriano's absence.
"It shouldn't, but it does," he said. "Throughout the course of the season, you're going to do things you didn't think possible -- both good and bad. Getting Sori back was huge, but there was never a doubt we'd start hitting again."
DeRosa had two hits and drove in five runs after going 3-for-5 with three RBIs the previous day.
The Cubs roughed up Brandon Backe (6-11) and will try to carry that momentum into a three-game weekend series with rival St. Louis. Backe allowed a career-high 11 runs and nine hits in 3 1/3 innings. He walked six, did not strike out a batter and paid for those control problems.
"Anything that was falling off the plate they didn't swing at, and anything that was up in the zone or over the plate they pretty much hit," Backe said.
Carlos Lee's three-run homer in the third capped a four-run burst that gave Houston a 4-1 lead, but the NL Central leaders responded in a big way in the bottom half, sending 11 batters to the plate. All eight runs came after Backe walked Aramis Ramirez and Jim Edmonds to load the bases with two outs.
DeRosa drove a 1-1 pitch to left-center for his second grand slam this season.
Kosuke Fukudome doubled down the right-field line and, after Soto was intentionally walked, came around on pitcher Jason Marquis' double off the right-field wall. Soriano then drove the first pitch out to left for his 21st homer, making it 9-4.
All that offense helped Marquis (7-7) win for the first time since beating the White Sox on June 21. The right-hander allowed four runs and six hits in 6 1/3 innings after going 0-4 in his previous six starts.
He escaped a bases-loaded jam in the fourth but did not allow a run after Lee hit his 27th homer.
"We could have swept the series," said Lance Berkman, who was 0-for-13 before an RBI single in the third. "We certainly could have won two out of three."
Cubs shortstop Ryan Theriot fouled a pitch off his left foot in the fifth and was replaced by Ronny Cedeno before the seventh. ... Cubs right-hander Jon Lieber, on the DL with a strained right foot, was back at Wrigley Field after giving up three runs and five hits in three innings Tuesday during a rehab outing with Class A Peoria. "Physically, I'm fine. It's just building up strength," said Lieber, who was not sure when he will return. ... After playing 20 games in 20 days, the Cubs will have their first day off since the All-Star break on Thursday. ... Geoff Blum started at shortstop for Houston instead of Miguel Tejada. ... Infielder Mark Loretta was unavailable because he was still sore from a collision at home plate against the New York Mets on Saturday.