CHICAGO -- Ryan Dempster got plenty accomplished in his short five-inning start. He ran his record at Wrigley Field to 7-0 and also contributed a two-out RBI double, his first extra-base hit since 2002.

Dempster and the Chicago Cubs seem to be having a really good time lately, especially at their cozy ballpark.

Alfonso Soriano drove in Dempster with a two-run homer and finished with three RBI, helping the Cubs beat the Colorado Rockies 5-4 Saturday for their sixth straight victory. Chicago also improved to 25-8 at home.

Talk about Friendly Confines.

"It's been fun for us and I'm sure it's been a blast for the fans to come to the park every day," Dempster said.

"We got to keep it going."

With the wind blowing out at 14 mph and gusting up to 20 mph, balls again had a jet stream to ride over the fence. The teams combined for seven homers Friday - four by Chicago and three by Colorado - and four more went out Saturday, three by the Rockies. But the defending NL champs still lost their sixth straight.

"It's hard to figure out. Poor execution. All phases of the game, we're just not doing enough to win," said Todd Helton, who homered for the second straight game.

Dempster (7-2) struggled with his command. He walked four, hit a batter with a pitch and was charged with three runs and three hits.

Manager Lou Piniella decided that Dempster, his closer-turned-starter who'd thrown 117 pitches in his previous outing, was done for the day after 93 pitches. Piniella plans to shorten some starts and rest players when possible as the Cubs head out on a West Coast trip after playing 33 home games the first two months. Chicago is 10-13 on the road so far.

"We'll keep guys as fresh as we can," Piniella said. "We knew we were going to play a lot of games early here at home and we knew it was important that we post wins with frequency here in our home ballpark. This team has done it."

After Dempster departed, three Cubs relievers combined for three hitless innings before Carlos Marmol worked the ninth for his third save in four chances.

Kosuke Fukudome backed Marmol with a nice catch in front of the right-field wall for the second out on a long drive by Omar Quintanilla. Scott Podsednik followed with a homer to right to cut it to 5-4 before Marmol struck out Willy Taveras to end the game.

Former Cub Glendon Rusch (1-3), making his first start since July 9, 2006, gave up nine hits and five runs in 4 2/3 innings.

Quintanilla hit his first major league homer, a two-run shot in the second, to give the Rockies the lead one day after they squandered an eight-run cushion in a 10-9 loss.

Chicago responded with three runs in the bottom half. Dempster hit an RBI double and Soriano followed with his 12th homer to make it 3-2.

Geovany Soto's RBI double, a ball that appeared to tip off the glove of center fielder Taveras, made it 4-2 in the third and Soriano added an RBI single in the fourth.

Helton's homer in the fifth cut the lead to 5-3.

First base umpire Brian O'Nora had to leave the game in the top of the second after hurting the back of his left leg -- apparently after running to the outfield the previous inning to make a ruling on a catch -- and was taken to a local hospital for an MRI exam. The game continued with three umps.

Rusch pitched three years with the Cubs and was released after his 2006 season was cut short by a blood clot in his lung. He made a comeback with the Padres earlier this season, pitching 12 games in relief, going 1-2 with a 6.41 ERA.

He later signed as a free agent with the Rockies, who purchased his contract from Triple-A Colorado Springs so he could pitch Saturday's game.

"It's pretty neat. It's been a long road for me missing last year and getting a chance to come back and pitch so it's pretty cool to do it here," Rusch said.

"I prepared myself to retire after that happened ... I was prepared to not pitch again and I was pleasantly surprised when I was able to come off the blood thinners after a year and be able to pitch again."

Dempster saluted his friend and former teammate Rusch, whom he planned to meet after the game.

"I think it is really remarkable. Here is a guy who had his career stopped short because of something that was non-baseball related, to have a blood clot in his lung and to sit out all that time and then come back," Dempster said. "I hate to see him lose, but I'm glad it was against us."

Notes

• Rockies LF Ryan Spilborghs, who was hit with a pitch in the third inning, came out in the sixth. He has a bruised left wrist and will be evaluated daily.
• Soriano was hit on the foot with a pitch in the eighth but was OK after the game. He was replaced in the outfield in the ninth.