CHICAGO – Carlos Zambrano’s pledge to himself and his teammates is a simple one. Pitch and play like you’ve still got a chance.

It would take one of the great miracles in baseball history to get the Chicago Cubs to the postseason. But they have played better ball in the last week and on Sunday completed a rare four-game sweep of the first-place St. Louis Cardinals behind Zambrano.

“I am one of the guys that thinks you never have to give up,” Zambrano said after outpitching Chris Carpenter to win his ninth straight decision as the Cubs beat the Cards 6-3.

“When you have that ‘X’ that says you’re eliminated, then you give up,” Zambrano said. “We’re still fighting for something. We still have a chance to do a lot of things.”

The Cubs (43-61) own their first four-game winning streak since capturing five straight last July.

And Chicago’s first four-game sweep of the Cardinals at Wrigley Field since 1972 left the Cardinals 0-7 this season at the Cubs’ home park. The Cubs also swept a three-game home series from the Cards in early April.

“That’s the million dollar question,” said second baseman Todd Walker. “Why can’t we do this all year long?”

Zambrano (12-3), who has not lost since May 31, allowed five hits, five walks and two runs with five strikeouts in six innings, facing a Cardinals lineup that didn’t start Albert Pujols. He was a late scratch with a hyperextended right elbow, but entered the game as pinch-hitter in the seventh.

Carpenter (10-5) lasted just four innings – his shortest start of the season – and gave up all five of his runs in the first two innings on a muggy day. He yielded a leadoff homer to Ronny Cedeno in the second and six hits.

“I felt fine, I just didn’t pitch real well,” Carpenter said. “I made a lot of bad pitches and left the ball in the middle of the plate.”

He said it’s obvious that despite their overall 58-46 record, the Cardinals have not played well against the Cubs this season.

“You look at the games we played. We haven’t pitched well, we made some defensive mistakes and haven’t gotten any big hits,” he said.

Trailing 5-0, St. Louis broke through in the fifth when it loaded the bases for a second time in the game as Aaron Miles opened with the Cardinals’ second hit and pitcher Jason Marquis hit a pinch-hit double. Zambrano walked Chris Duncan to load the bases and the Cardinals scored on Scott Rolen’s fielder’s choice grounder to third. Zambrano then fanned Jim Edmonds and pumped his fist.

Chicago made it 6-2 in the seventh on pinch-hitter John Mabry’s RBI single off Adam Wainwright.

When Todd Walker hit a grounder to short, David Eckstein threw home and catcher Molina’s tag appeared to get Blanco at the plate, but umpire Marvin Hudson ruled him safe, giving the Cubs a 4-0 lead and bringing Tony La Russa out for an argument. Ramirez then delivered an RBI single to right.

Carpenter had won four straight decisions entering the game.

The Cardinals made it 6-3 in the ninth on an RBI single by Rolen after Duncan’s triple.