Cardinals 11, Cubs 1
"You know the old saying. If you're going to win one out of three, win the last one," St. Louis manager Tony La Russa said.
With the Cardinals nursing a 1-0 lead, Duncan came up with one out and the bases loaded in the fifth. He hit a 2-2 pitch for his 20th homer and his second grand slam of the season to give the Cardinals some breathing room.
"I was waiting for something out over the plate and I just wanted to give myself a shot," Duncan said. "I knew I hit it good but I thought I might have hit it too high."
Pujols, who did not meet with the media after the game, was also an offensive force, driving in five runs, tying his season high. He last did it on June 10 against the Los Angeles Angels.
Chicago starter Jason Marquis (7-6) allowed six runs in five innings. He walked four and struck out just one. Marquis had beaten his former teammates in two earlier starts this season.
St. Louis scored five runs on two hits in the fifth for a 6-0 lead. Aaron Miles led off with a single and Marquis walked Looper, who was trying to bunt. After a sacrifice bunt advanced the runners, Marquis walked Jim Edmonds. With the bases loaded, Marquis hit Pujols to score Miles and set the stage for Duncan.
"I just wanted to put the ball in play," Duncan said.
The Cubs, winners of the first two games of the series, remained two games behind Milwaukee in the NL Central.
"It wasn't a good game," Chicago manager Lou Piniella said. "Hey look, we won two out of three here. Let's go to Cincinnati and try to do the same."
The defending World Series champion Cardinals are eight games back in third place. The Brewers come to St. Louis for four games beginning Friday.
Scott Rolen hit his sixth homer with two outs in the fourth, giving the Cardinals a 1-0 lead. It was his second homer in four days. Last week, Rolen missed four games after receiving a cortisone injection in his left shoulder to help with inflammation and tightness. It was Rolen's first homer at Busch Stadium since June 18 -- a span of 97 at-bats.
In the sixth against Billy Petrick, the Cards scored four runs. Yadier Molina and Miles singled. Molina then stole his first base of the season, fourth in his career. Looper hit a bloop single to left, scoring Molina. With two outs, Pujols slammed the ball into the right-field bleachers for his first hit in the series.
It was Pujols' seventh home run since the All-Star break.
"He's a special player. Everybody knows that," Marquis said. "Everbody goes through slumps but players of that magnitude minimize how long they're in them."
Looper (8-8) gave up a run and five hits to win for the second time in three starts. He has a 1.38 ERA in his eight victories.
"I felt good today. I made a lot of good pitches," Looper said.
Derrek Lee hit a solo homer in the sixth for Chicago's only run. It was his first homer on the road.
Chicago is 14-4 in its last 18 games. ... It was Chicago's first loss in five games at Busch Stadium this year. Overall, the Cardinals are 41-20 at home against the Cubs this decade. ... La Russa said he started Miles at second base instead of Adam Kennedy because Miles was 4-for-8 against Marquis. ... Duncan's other grand slam came June 16 at Oakland. ... The Cardinals passed the 2 million mark in attendance with a sold-out crowd of 45,308. It marked the 26th consecutive St. Louis has topped 2 million in attendance.