The Cardinals know that their margin for error in the National League Central race shrinks with every passing loss. Good thing ace Chris Carpenter has been near perfect when facing the Pirates.

Carpenter will look to continue his season turnaround and get St. Louis even in its three-game series with Pittsburgh tonight at PNC Park.

The 36-year-old Carpenter is an excellent 12-2 in his career when facing the Pirates, pitching to a 2.24 earned run average in that span. He beat them the last time he faced them on July 22, allowing four runs over eight innings in the Steel City.

After a slow start to the season, Carpenter has found his ace form. He has won seven of his past eight decisions and can win a third straight start this evening after beating the Brewers on Thursday. Carpenter gave up 10 hits and three walks over eight innings, but limited the damage to just a pair of runs.

The right-hander has a 2.60 ERA in his last 10 starts and has pushed his season mark to .500 at 8-8 with a 3.68 ERA.

After splitting a six-game homestand, the Cardinals were on the wrong end of a 6-2 decision in Pittsburgh last night. The defeat dropped St. Louis six games behind first-place Milwaukee in the NL Central after the Brewers shut out the Dodgers.

Jake Westbrook couldn't make it out of the sixth inning, giving up five runs -- four earned -- on nine hits in 5 2/3 frames of work.

"They definitely capitalized on the mistakes I made tonight," Westbrook said. "I felt strong about my sinker. It's a little frustrating to get hurt with my fifth-best pitch. I needed to be good tonight and I wasn't."

Ryan Doumit was locked in on Monday for the Pirates, highlighting a 4-for-4 night at the plate with a three-run homer in the fourth inning. The big game lifted the catcher's average 25 points to .302 in 42 games this year.

"Big night for Ryan swinging the bat," Pirates manager Clint Hurdle said. "He squared up four balls."

Xavier Paul also homered and Neil Walker added an RBI double for Pittsburgh, which snapped a three-game slide with just its third victory in 17 games.

James McDonald gave up two runs on six hits in 5 2/3 innings to earn the win.

The Bucs' Jeff Karstens will try to carry over the momentum from his last start when he snapped a four-game winless streak (0-2) with a solid outing in San Francisco. Facing the Giants on Wednesday, the righty struck out a career- high nine and gave up two runs over six innings.

It was a nice rebound effort for Karstens, who was blitzed for nine runs over just 3 1/3 frames five days earlier in a setback to the Padres. He won for the sixth time in eight decisions on Wednesday, moving to 9-6 with a 3.04 ERA this season.

The 28-year-old is 1-1 with a 1.40 ERA in four career meetings with the Cardinals, with the lone relief outing coming this year on April 5.

The Pirates own a slight 4-3 advantage in their 2011 season series with the Cardinals.