The Pirates (47-41) have won an NL-best 12 of 15 and are 11-5 away from home since May 29. They claimed their first series sweep of the season Sunday with a 6-2 home victory over Philadelphia as Jeff Locke limited the Phillies to two runs and three hits over eight innings.
"I didn't know we didn't have a sweep all season," Locke said. "It feels good, especially (against) a team like those guys over there."
Andrew McCutchen was 2 for 4 with his second triple in three games and is batting .382 during Pittsburgh's 12-3 run with eight extra-base hits and 12 RBIs. He's also 13 for 34 with seven extra-base hits versus Wainwright, but the right-hander has won two of his last three starts against the Pirates.
Wainwright (11-4, 1.89 ERA), who has split two starts against them this year, had gone 1-2 with a 6.00 ERA in his five previous matchups before limiting Pittsburgh to two runs over 22 innings in the last three.
Since surrendering a season-high seven runs in 4 1-3 innings in a 9-4 loss to San Francisco on May 30, Wainwright is 3-1 with a 0.93 ERA in five starts despite getting only nine runs of support in that span.
He avenged that lopsided defeat against the Giants on Wednesday, throwing 7 2-3 innings of four-hit ball in a 2-0 victory. Wainwright - trying to become the NL's first 12-game winner - pitched to contact and finished with a season-low one strikeout.
"I'm getting outs, so why change? When you start thinking about strikeouts, then you start going deeper into counts," Wainwright said. "Guys were making great plays and laying out left and right."
The Cardinals (47-42) are one-half game behind the second-place Pirates but have dropped two straight following Sunday's 8-4 loss to Miami. St. Louis has dropped six of 10, averaging 2.5 runs in that span.
"All we can do is stick with our approach and go up there and get the barrel on the balls, and that's what we're doing," said Matt Adams, who had a career-high four hits. "We're just hitting it right at people right now."
The Cardinals figure to fare better against Morton (5-9, 3.30), whose winless streak versus St. Louis reached nine starts in a 6-5 home loss on May 11. Morton, who gave up four runs - one earned - over six innings, is 0-7 with a 5.91 ERA since beating the Cardinals on April 4, 2011.
The right-hander is 2-6 in nine road outings this year but gave up one run over six innings in a 5-1 home victory versus Arizona on Wednesday.
Yadier Molina is 10 for 22 versus Morton while Allen Craig is 11 for 21. Jon Jay, batting .182 over his last 12 games, is 9 for 19.
Jhonny Peralta is batting .370 with four homers and seven RBIs over his last eight matchups against Pittsburgh.
Russell Martin is 9 for 22 against Wainwright.
The Pirates own a 5-4 series edge this season, though they've dropped six of seven in St. Louis and were shut out twice in a three-game set there in April.