Gio Gonzalez and the rest of the rotation have been vital to the Washington Nationals' lead in the NL East.
Wainwright looks to extend the longest winning streak of his career when he starts opposite Gonzalez on Friday night in the nation's capital.
Gonzalez (16-7, 3.28 ERA) is among the contenders for the NL Cy Young Award, ranking among the league leaders in wins and strikeouts (168) while yielding just eight homers.
The left-hander, who has already matched his career high in victories from last year with Oakland, is part of a Nationals rotation that leads the NL with a 3.27 ERA and a .236 opponents' average.
Edwin Jackson built on that success in the opener of this four-game series Thursday, allowing an unearned run and four hits with 10 strikeouts in eight innings as the Nationals (79-51) cruised to an 8-1 victory.
Washington's lead atop the East is 5 1/2 games over second-place Atlanta.
Wainwright (13-10, 3.63) is having an impact in the wild-card race for the Cardinals (71-60), whose lead for the second spot is down to a half-game over Pittsburgh.
The right-hander will try to continue his recent dominance to provide some breathing room. He's 6-0 with a 1.80 ERA in his last seven starts, emerging victorious in each of his last five.
He allowed two runs in 5 2-3 innings Sunday in an 8-2 win at Cincinnati. That performance came five days after he matched his carer high with 12 strikeouts in a five-hit shutout of Houston.
"I wanted to take my team further in the game than that, but I get it," Wainwright said Sunday. "I had a couple of games in a row that I threw a lot of pitches."
He's 3-2 with a 2.83 ERA in eight games - six starts - against the Nationals, but hasn't faced them since a loss at Washington on Aug. 29, 2010.
St. Louis may need another strong performance from Wainwright since the team has been outscored 22-1 while hitting .149 during a three-game losing streak.
"Nothing we can put our finger on," manager Mike Matheny said. "No explanation at this point."
To make matters, St. Louis might be without its starting shortstop for the rest of the season. Rafael Furcal suffered a strained right elbow while making a pair of throws in the sixth inning Thursday, and he'll undergo an MRI on Friday.
Furcal described hearing a "pop" in the elbow, and the team fears he might have damaged his ulnar collateral ligament.
"It's very concerning," outfielder Matt Holliday told the team's official website. "He's one of the best shortstops defensively in the league. Even when he doesn't swing the bat well, he brings a lot to the team."
With the offense struggling, the Cardinals really use some production from Holliday and Allen Craig, who are a combined 1 for 23 during the skid.
Holliday is batting .424 over his last nine meetings with Washington, but Craig has fanned five times while going hitless in nine at-bats in four career matchups.
They'll get their first look at Gonzalez, who is trying to rebound from Saturday's 4-2 loss at Philadelphia. He allowed three runs - two in the first - with seven strikeouts in six innings after winning each of his previous three outings with a 2.53 ERA.
Three of Bryce Harper's four hits in the past two games have gone for homers. The rookie has a .314 average with four homers and nine RBIs in his past nine home games.