CHICAGO -- The bright lights were on at Wrigley Field, the skies darkening above a game approaching the four-hour mark.

The Cubs and Cardinals had combined to use 12 pitchers and seven pinch-hitters in a seemingly endless series of matchups. By the 11th inning on Saturday, St. Louis was down to lefty Dennys Reyes.

Aramis Ramirez wasn't about to go 0-for-6.

The Cubs' clutch third baseman blasted a Reyes fastball to left-center field. The two-run walk-off home run finally decided a 7-5 victory. It was the first walk-off homer hit by a National League player this season.

"You don't want to be in that position," Ramirez said. "You want to win the game in nine innings, but we made things happen.

"I've never been 0-for-6 before. I got to do something. I was thinking about bunting there, too."

Ramirez could crack jokes in the clubhouse afterward because the Cubs won the battle of the bullpens in front of 40,878 fans. Angel Guzman threw a scoreless 11th inning to earn his first career win, but that was part of a much bigger picture.

Reliever Carlos Marmol, who inherited the two batters Neal Cotts walked to lead off the seventh, used 12 pitches to escape one jam unscathed and preserve a 5-4 lead.

In opening the eighth, Marmol allowed back-to-back doubles to Chris Duncan and Yadier Molina. Just like that, the game was tied, 5-5.

Cubs closer Kevin Gregg bailed out his setup man. Gregg struck out the next two batters and got Skip Schumaker to ground out. He also worked a perfect ninth. Aaron Heilman followed with a scoreless 10th.

"That's what's it's all about," said Cubs starter Ryan Dempster, the converted closer. "[It's] coming in with runners on base, getting that adrenaline going and getting some big outs in some big situations.

"I put us in a little bit of a hole and the guys kept fighting and scored some runs. And what a job the bullpen did of picking each other up."

For those in Cubs gear who came to Wrigleyville on a clear 69-degree afternoon, it was a jam-packed day for the city's sports fans. By the time Dempster threw the first pitch at 2:41 p.m. CT, the Bulls had already worked overtime to upset the second-seeded Celtics in the first game of their opening-round playoff series.

Dempster, a huge hockey fan growing up in Canada, was planning to attend Game 2 of the Blackhawks-Flames series on Saturday night at the United Center. Even Jay Cutler, the newly acquired Bears quarterback, was in the house on Saturday to sing "Take Me Out to the Ball Game."

Dempster went six innings, keeping the Cubs in the game after giving up four early runs. Once Khalil Greene led off the fourth inning with a solo home run to give the Cardinals a 4-1 lead, Dempster proceeded to retire nine of the final 10 hitters he faced. That seemed like a very long time ago by the time Ramirez made his dramatic swing.

But others were also responsible for this win. Derrek Lee stroked the two-run double that tied the game, 4-4, in the fifth. Aaron Miles, a Cardinal for the past three seasons, hit a go-ahead RBI single in the sixth.

The Cubs (7-4) and Cardinals (8-5) will do it all over again Sunday night.

"The fans have been treated to pretty good baseball here so far in this St. Louis series," said Cubs manager Lou Piniella, who almost sounded like it was too much after Friday's 8-7 comeback victory. "You don't have to do this too often to win it. It's wonderful and it's exciting. The home team fans [will] frequent a few of the establishments over here in Wrigleyville. But let's win the conventional way."