A day after tying a franchise record by using nine pitchers in a 17-inning game, manager Craig Counsell was bold in using his bullpen again.
This one, the Milwaukee Brewers finished a lot faster.
''I really wanted to stay away from a couple guys, so they're available and got something in the tank when we need them,'' Counsell said.
Fiers (2-5) allowed four hits in six innings, one shy of his season high, and won for the first time in six starts since May 2 at Chicago.
''The middle four innings was kind of vintage him,'' Counsell said. ''Lots of good fastballs and kind of lazy flyballs.''
Jonathan Broxton, Neal Cotts, James Jeffress and Francisco Rodriguez combined to allow four hits without walking a batter in Milwaukee's fourth shutout of the season. Rodriguez finished for his ninth save.
Jaime Garcia (1-2) worked seven sterling innings and Kolten Wong and Mark Reynolds had two singles apiece for the Cardinals, shut out for the fifth time but first time at home where they're among the best in the league at 20-7.
''Who would have thought two singles in the first would decide the game?'' manager Mike Matheny said. ''It's a shame. Great outing.''
Garcia has a 2.70 ERA in three starts since returning from thoracic outlet surgery. He totaled 16 starts the previous two seasons.
''Am I encouraged by the way I'm feeling and competing? Yeah,'' Garcia said. ''But I wouldn't say happy. It hasn't been in my mind the whole time. I'm just going out there and competing.''
Wong made an outstanding play at second base, leaping to snare a high chopper by Jason Rogers that skipped off the front of the mound and making the throw to end the ninth.
Jean Segura singled to open the game and scored on a two-out single by Gomez. The Brewers had two more runners in scoring position the rest of the way.
''It was the kind of game we needed from Mike, and he did a heck of a job,'' Counsell said. ''He pitched into some jams, but he was himself.''
Garcia retired the side in order the next five innings, once with the help of a double play that bailed out his throwing error. He worked seven innings for the second time in his three starts and allowed just three hits with no walks.
Brewers: Catcher Johnathan Lucroy was activated from the DL after missing 38 games with a broken big left toe. He was robbed of a hit by center fielder Jon Jay's running catch in the first then grounded out his last three trips.
Cardinals: Matt Holliday was back in the lineup after missing 1 1-2 games due to flu-like symptoms and extended his franchise record reaching base safely in 45 straight games to start the season with a first-inning walk.
Lance Lynn is getting just 2.82 runs of support per start from the Cardinals, third-lowest in the league. Tyler Cravy, whose contract was purchased from Triple-A Colorado Springs, will make his major league debut for the Brewers, whose pitching staff is worn thin after a 17-inning victory over Arizona on Sunday. The decision wasn't finalized until after the game, because Counsell said he might have had to use him.
Matt Carpenter was 0 for 4 with two strikeouts and is 2 for 18 against Fiers.
Link to box score: Milwaukee (18-34) 1 at St. Louis (33-18) 0