A shaky performance could be difficult to overcome without two of Milwaukee's best offensive players.
Owner of baseball's best record, Milwaukee (18-7) had won three straight and seven of eight before falling 4-0 to the Cubs on Sunday. The Brewers failed to get much going without Braun and Segura, finishing with three hits.
Braun is dealing with a strained chest muscle, and Segura had a partially closed right eye and bruised right cheek after getting hit during a practice swing by Braun on Saturday. Both players hope to return during the team's seven-game road trip.
"We don't expect them to be (out) real long, but you never know," manager Ron Roenicke told MLB's official website.
The Brewers will try to bounce back behind Gallardo (2-0, 1.42 ERA), who has allowed two runs or fewer in each of his first five outings.
"I've just been consistent," he said. "That was one of my main focuses in spring training, and I've been able to do that. It's a matter of keeping it going throughout the year."
After opening with back-to-back wins, Gallardo has gone without a decision in his last three starts while receiving a combined five runs of support. He yielded one run and five hits over seven innings in Tuesday's 2-1, 12-inning loss to San Diego.
"It takes a lot to keep the lineup that we have to one run," Gallardo said. "As far as being a pitcher, we know the guys can hit. ... You just have to keep us in the ballgame and wait for that to happen."
Gallardo hasn't given the Brewers much of a chance in his last 10 starts - including playoffs - versus the Cardinals, a stretch during which he's gone 0-8 with an 8.17 ERA. He is 1-11 with a 6.46 ERA in 17 regular-season starts against St. Louis, his worst ERA and most losses against any team he's faced more than once.
The Cardinals counter with Michael Wacha (2-2, 2.10), who posted mixed results in Wednesday's 3-2 road loss to the Mets. The right-hander set career highs with 10 strikeouts and five walks in four innings, the shortest of his 14 regular-season starts.
Wacha's first nine outs all came via strikeout, but he walked three in the fourth to match his total from his first four outings combined.
"I don't credit it for losing my mechanics in that inning," Wacha said of the 41-mph winds. "You have to be more mentally tough than I was tonight. Walking in two runs is just unacceptable.
"Looking at the video, mechanically, my arm was dragging. I just wasn't in sync. I felt good through the first 30 pitches, not really sure what happened after that."
Wacha could be looking forward to getting back home, where he's compiled a 1.04 ERA in winning five consecutive outings, including the postseason. Monday marks his first start against the Brewers.
St. Louis (14-12) took two of three from Pittsburgh to open a six-game homestand, winning 7-0 on Sunday. Jhonny Peralta snapped the team's 366-at-bat homerless drought with a solo shot in the fifth inning, then belted a three-run homer in the sixth.
Peralta has six of the team's 14 homers, the most by a Cardinals shortstop in April. He went 5 for 12 with two long balls as St. Louis took two of three at Milwaukee earlier this month.