Adam Wainwright can move into a tie for the National League lead in victories Saturday night.
More importantly, with a strong outing at Busch Stadium, the St. Louis right- hander can put the Cardinals back into first place in the Central Division.
The Cardinals, who won 12-8 over the Pirates to open this three-game set Friday night, are just a half-game behind first-place Pittsburgh.
"This is what you play for, this is why you grind out a whole season so that when you get into this part of the season you have a chance to play for a postseason, play for a division title," Cardinals second baseman Matt Carpenter said. "We're in a really good spot."
Wainwright, who makes his team-leading 30th start of the season, has lost his last two outings, both against the Reds. In those contests, Wainwright allowed a combined 17 hits and 15 runs in eight innings.
Wainwright has a career mark of 8-4 with a 5.11 ERA in 21 games (17 starts) against Pittsburgh.
Jeff Locke, who has gone 1-2 with a 6.18 ERA in eight starts since the All- Star break, counters for the Pirates. The lefty hasn't won in his last seven starts since posting a victory at Cincinnati on July 21. Locke is 1-0 with a 3.27 ERA in two starts versus the Cardinals.
Jon Jay went 3-for-4 with three runs scored and three RBI for the Cardinals Friday night. Matt Holliday and Carlos Beltran knocked in two runs apiece and Carpenter doubled, tripled, scored three runs and drove in another for St. Louis, which began a nine-game homestand Friday on a high note after a disappointing 2-5 stretch in Pittsburgh and Cincinnati.
Josh Harrison smacked a two-run homer for the Pirates, but only after the Cardinals blew the game open with a seven-run seventh inning that started with nine consecutive hits, highlighted by Yadier Molina's three-run homer.
Joe Kelly (8-3) gave up eight hits and three walks but stranded 10 Pirates and held them to one run over his six innings of work. The right-hander has won his last five starts and eight straight decisions overall.
St. Louis is on top in the NL wild card race.
Pirates starter A.J. Burnett (7-10) was knocked out early after surrendering five runs on six hits in the first three innings.
"I felt like I could have done more," Burnett said. "I felt like I could have stayed out there longer and kept us in it, but it's not my choice, not my decision."
Pittsburgh is 10-7 against the Cardinals this season.