And with the 4-3 loss to the Brewers, they relinquished first place in the National League Central for the first time since May 19.
"It means that we're no longer in first place," Cardinals manager Tony La Russa said. "We're no longer in first place, and this is June, and now we have to be ready for Washington on Tuesday.
"I don't want to get melodramatic," he continued. "We came here to win a series and we got beat in the series. They out-managed us, they out-played us and if you do those little things, you usually have a better score."
After an off-day on Monday, the team begins the last of a three-series road trip against the Nationals on Tuesday.
"We have an off-day, and hopefully we can be able to enjoy that," outfielder Jon Jay said. "And start winning some series."
Left-hander Jaime Garcia will toe the rubber against right-hander Yunesky Maya.
After winning four consecutive games earlier in the season, Garcia has struggled of late, dropping two of his past three starts and not lasting more than five innings in three of his past four.
The 24-year-old was tagged with the loss after pitching five innings against the Astros on Wednesday, allowing three runs on seven hits.
He beat the Nationals in the nightcap of a doubleheader on April 20, allowing three runs (one earned) on four hits in five innings.
In two career starts against Washington, he is 2-0 with a 0.87 ERA.
After dropping the first game of a four-game set to the Padres on Thursday, the Nationals won three straight and enter Tuesday's game fresh off a 2-0 victory on Sunday.
Opposing Garcia is Maya, who is 0-1 with a 5.40 ERA in three starts this season.
Maya pitched six innings of one-run ball against the Giants on Wednesday, finishing with a no-decision in his best outing of the season.
Cardinals: Injuries are healing
Outfielder Matt Holliday and starting pitcher Kyle McClellan are both expected to return from the disabled list this week. Holliday's expected return is on Thursday, while McClellan is penciled in for a starting assignment against the Nationals on Wednesday.
Nationals: Defense is dominating
With an errorless game in Sunday's victory, Washington completed its West Coast trip without making an error.
With seven scoreless innings on Sunday, Jordan Zimmermann won three games on the road trip, allowing three runs or fewer and pitching seven innings in all of them.
Third baseman Ryan Zimmerman was activated from the DL before the game. He missed 58 games with an abdominal injury.
Ian Desmond is hitting .667 in three at-bats against Garcia, and no one on the Nationals has hit a homer off the left-hander.
Maya has never faced the Cardinals.