The Nationals will try to solve Wainwright and end a four-game skid to the Cardinals on Monday night.
St. Louis (91-65), which beat Washington (84-72) in last season's Division Series, is headed back to the playoffs after clinching a spot thanks to the Nationals' 4-2 loss to Miami in the opener of Sunday's doubleheader.
The Cardinals fell 6-4 at Milwaukee on Sunday but lead Cincinnati and Pittsburgh by two games in the NL Central with six to go in the regular season.
The Nationals are trying to catch the Reds and Pirates, the league's wild-card co-leaders. They trail by five games with six to play after winning the second game of Sunday's twinbill 5-4.
Despite overwhelming odds, the Nationals aren't giving up on the postseason.
"We aren't finished. I take nothing for granted," manager Davey Johnson said. "I still think we got a good shot. We need to win them all. We do. Hey, I've been one strike, two runs down, one strike away, and we've come back. So don't lose the faith."
Facing Wainwright (17-9, 2.98 ERA) isn't likely to help Washington.
The Cardinals' ace has won his last two starts against the Nationals, yielding one run with 14 strikeouts in 14 1/3 innings. He beat them again April 23, coming two outs shy of a complete game while fanning nine in a 2-0 road victory.
Wainwright is 2-0 with a 1.59 ERA in his last three starts overall. The right-hander is second in the league in wins, and among the leaders in ERA, strikeouts (209) and WHIP (1.08).
Wainwright allowed three runs in 7 2/3 innings and proved to be just as capable at the plate in Wednesday's 4-3 win at Colorado. He matched his career high with three hits and added two RBIs, one coming on his fourth double of the season.
"I always brag that the starting pitchers are the best athletes on the field," Wainwright said.
Matt Carpenter may feel differently, as he's batting .407 with seven doubles, nine RBIs and 13 runs in the past 14 games. The second baseman homered Sunday and is batting .324 as he chases Colorado's Michael Cuddyer (.334) and Chris Johnson (.329) of Atlanta for the NL batting title.
The Nationals are hoping
Tanner Roark (7-0, 1.08) can slow down Carpenter in his first meeting with the Cardinals, and continue his dazzling run.
The rookie right-hander has a 0.95 ERA while winning all three of his starts since being inserted as the fifth starter. He was superb again Tuesday, yielding two hits in seven innings of a 4-0 win over Atlanta.
"It's not smoke and mirrors right now," first baseman Adam LaRoche said. "When you get guys coming down to first talking about how good his stuff is, some really good hitters that are praising him, it says a lot."