A victory Saturday night would move the Brewers within five games of a playoff spot for the first time in almost two months.
Milwaukee (68-70) arrived in St. Louis having won 13 of 17 to trim 5 1/2 games off its deficit in the wild-card race and pull within seven of the Cardinals (74-64). It picked up another game Friday, thanks to Ryan Braun's 13th-inning homer providing a 5-4 victory.
"We've been a resilient team all year," Braun said. "We're realistic about where we're at. We got to play great baseball the rest of the way, but by no means are we out of it. A game like tonight can be the type of thing that can propel you to a winning streak, so hopefully it will do it for us."
The Brewers, who overcame a rain delay of 2 hours, 20 minutes and withstood a game-tying, two-run homer by Yadier Molina in the eighth inning, haven't been within five games of a playoff spot since July 18, when they were 5 1/2 back of Atlanta for the NL's second wild card.
St. Louis, which has lost seven of 10, still owns a 1 1/2-game lead for the second wild-card spot.
''It's extremely frustrating,'' manager Mike Matheny said. ''We had our chances and just couldn't come through.''
Braun, whose homer also made him the first player in Brewers history with five 100-RBI seasons, has been instrumental to his team's surge. He is batting .396 with four homers, six doubles and 15 RBIs in his last 12 games, and his next home run will be his 200th.
Braun and several of his teammates could be poised for big games Saturday against scheduled starter Jake Westbrook (13-10, 3.93 ERA).
The reigning NL MVP is 8 for 16 with a homer and triple lifetime against Westbrook, while Corey Hart is batting .313 with two home runs and one double in 16 at-bats. Aramis Ramirez has been out since Wednesday with a minor back injury but is hopeful to play Saturday, and is 6 for 11 with two doubles lifetime against Westbrook.
After yielding 12 runs in 10 innings in back-to-back starts against Houston and Pittsburgh, Westbrook pitched better Sunday in Washington, allowing two runs and nine hits in 5 1-3 innings, but St. Louis ended up losing 4-3.
"It's a step in the right direction and something I can build off of," the right-hander told the Cardinals' official website.
In his lone start of the season against Milwaukee on April 27, he gave up one run and seven hits in seven innings of a 13-1 victory.
The Brewers counter with Mike Fiers (8-7, 3.11), who tries to put another disappointing start behind him.
In Miami on Monday, the South Florida native allowed six runs - four earned - six hits and four walks in 3 1-3 innings in a 7-3 loss. Both of the unearned runs were results of two errors by the rookie right-hander, who gave up five runs and five hits - all singles - in the fourth.
Fiers has a 7.40 ERA over his last five starts after posting a 1.82 ERA in his first 12.
His lone start of the season against the Cardinals came when things were going well. He gave up four hits in seven scoreless innings versus St. Louis on July 16, but the Brewers ended up losing 3-2. Molina had one of those hits - a double - and has feasted on Milwaukee pitching this season, batting .377 with three home runs.