The Nationals (83-67) evened the series with a 6-2 win on Tuesday night. Washington has a 1 1/2 game over the Chicago Cubs and Milwaukee in the National League wild card race.
St. Louis (84-67) holds a two-game lead over the Cubs and Brewers in the NL Central.
Wainwright (12-9, 4.00 ERA) is 5-1 with a 2.61 ERA in his past seven starts, and he has allowed one run over his past three starts, covering 20 innings.
In his latest outing, Wainwright pitched six scoreless innings in a Friday win against Milwaukee. He gave up two hits and struck out seven with three walks. Wainwright has won seven of his past nine decisions.
"We made an adjustment to my pregame routine, and my last three or four outings have been dramatically different with my energy level out on the field," Wainwright told the St. Louis Post-Dispatch.
Against the Nationals, Wainwright is 9-4 with a 3.34 ERA in 16 games, 14 of them starts. He beat the Nationals on April 30 when he gave up two runs on six hits over 6 1/3 innings.
Washington right-hander Max Scherzer (10-6, 2.65 ERA) gave up three runs on seven hits, leaving after five innings and 99 pitches in his latest outing, a Friday loss to the Atlanta Braves. It was his first defeat since May 17.
Since returning from the injured list in late August after recovering from a mid-back strain, Scherzer is 1-1 with a 3.91 ERA in five starts.
"It's new, but there's no excuses in this league," Scherzer said of coming back from a rare trip to the IL. "You've got to post, and you've got to go out there with everything you've got, and you've got to execute. Everything's on the line every single time you take the mound. This is Major League Baseball."
Scherzer, a St. Louis native, is 2-5 with a 2.95 ERA in 10 career starts against the Cardinals. He lost to them on May 1 when he allowed three runs on eight hits over seven innings.
Nationals manager Davey Martinez was released from the hospital Tuesday following a minor heart procedure but remained at his home in Washington. Bench coach Chip Hale is guiding the Nationals on an interim basis.
Kendrick also had a triple, single and a walk, and Victor Robles added two RBI singles for the Nationals, who improved to 7-9 in September.
Washington's bullpen provided three scoreless innings, one by Fernando Rodney and two by Daniel Hudson.
"It's that time of year," Hudson told MASN.com. "We've got to ride hot hands and just try to get wins any way we can. Whether that's me throwing the eighth and ninth, or Rodney or (Sean Doolittle) or whoever. It's just next man up. Try to ride the hot hands and get these W's, 'cause we really need them right now with this wild-card race being so tight."
--Field Level Media