By the time Chris Carpenter takes the hill tonight for year contract extension under his belt. As the ink dries, he'll be trying to extend his club's playoff chances.

Carpenter looks to get the Cards back into the win column tonight after they suffered a disappointing loss to the Pittsburgh Pirates on Monday night in the opener of a three-game series.

St. Louis carried a season-best five-game winning streak into last night's game and had won 12 of 16 before suffering a 6-5 loss. The Cardinals led late before the Pirates rallied for three runs in the eighth inning to go ahead.

Pedro Ciriaco hit a two-run double during the big frame and Neil Walker had three hits for the Pirates, who halted a three-game slide.

"He just battled in that at-bat," said Pittsburgh manager Clint Hurdle about Ciriaco. "He's continuing to grow and has worked hard to make the right adjustments. It was a big moment for him and I'm happy for him."

Albert Pujols drove in three runs, two on his 35th homer of the season, but couldn't prevent St. Louis from falling 6 1/2 games behind idle Milwaukee for first place in the National League Central. The Brewers did stay 4 1/2 games behind the wild card-leading Braves after their loss to Florida on Monday.

The Cardinals had won four of their previous five over the Pirates, but have now split 14 meetings with them this season.

"It's tough and it's going to happen from time to time," said starter Kyle Lohse. "We just have to come back out here tomorrow and try to win the series."

The first step is evening the set tonight and the Cardinals will try to do that behind Carpenter, who will reportedly receive a contract extension as early as today. The move comes after one of Carpenter's best starts of the season, a four-hit shutout of the Brewers on Wednesday.

"I'm not going to say yes or no," Carpenter told St. Louis' website of the possible extension. "There's obviously something going on, but it's not 100- percent done yet, and I don't want to jinx it."

The right-hander had allowed six runs in each of his previous two outings before shutting down the Brewers. It was his first shutout in exactly two years and 14th of his career, evening his season record to 9-9 with a 3.75 earned run average in 30 starts.

"I don't even know what the numbers are, I just know tonight was an important game to win," Carpenter said. "We're going to go out all the way to the end."

One of Carpenter's recent rough outings was against Pittsburgh on Aug. 27, when he gave up six runs over five innings of a loss. It was just the 36-year- old's third defeat in 15 career decisions against the Pirates and he still has a solid 2.64 career ERA against them.

Jeff Karstens will make his return to the hill tonight after having his last two starts skipped due to arm soreness and fatigue. He hasn't started since Aug. 28, when he was touched for five runs on nine hits and two walks over 3 2/3 innings of work versus the Cardinals. The righty gave up three runs in the first inning and a pair of RBI singles to Ryan Theriot in the game.

Karstens, 28, is 9-8 with a 3.32 ERA on the season and 1-2 with a 3.49 ERA against the Cardinals lifetime.