"They're all crucial," Milwaukee manager Ron Roenicke said. "We know that, but you've just got to go out and play. I thought that we played a good game today."
Milwaukee has won 25 of its last 32 games. Washington leads the NL East by 4 1/2 games over Atlanta. The Nats' magic number to clinch the division remains at six.
Reliever Brandon Kintzler (3-0) pitched a scoreless sixth inning, striking out Kurt Suzuki with the bases loaded. John Axford recorded the final out with two runners on for his 33rd save.
"It's fun. All these games are fun to watch from back there," Kintzler said of the bullpen. "Then suddenly you're in the ballgame. It's intense. It's something I've been thinking about the whole year, hoping I'd be a part of."
Ryan Mattheus (5-3) allowed three earned runs on four hits.
Milwaukee broke a 2-all tie in the seventh. Weeks singled and Ryan Braun grounded into a forceout. Ramirez doubled to right, putting runners on second and third.
After Corey Hart was walked intentionally, Lucroy hit a grounder up the middle. Shortstop Ian Desmond made a diving stop, but couldn't make the play at second and the Brewers led 3-2 with the bases still loaded.
The next batter, Carlos Gomez, hit a fly ball to right, but Jayson Werth lost it in the sun. Gomez wound with an RBI single and another run scored on Jean Segura's groundout.
"It's a tough sun. There's no doubt about it," Nationals manager Davey Johnson said.
The Brewers added a run in the eighth on Braun's sac fly.
Milwaukee took a 2-0 lead in the fourth. Braun led off with a fly ball to straightaway center and when Bryce Harper lost the ball in the sun, it dropped in and Braun ended up on second with a double. The next batter, Ramirez, hit a fly that Harper had trouble with, but caught.
"You can't catch what you can't see. Nothing you can do about it. The sun monster got me," Harper said.
In other games: *
At San Francisco, Yonder Alonso's two-run single in the seventh inning snapped a tie and helped the San Diego Padres beat the Giants, 6-4. The Giants rested their regulars a day after clinching the NL West title.
* At New York, Ruben Tejada singled home the winning run with two outs in the ninth inning to give the Mets a 3-2 victory over Miami.
* At Denver, Aaron Hill hit a tiebreaking three-run homer in the eighth inning and the Arizona Diamondbacks beat Colorado, 10-7, the Rockies' season-high ninth straight loss.
* At Houston, A.J. Burnett (16-8) allowed one run in eight innings, and Josh Harrison tied a career high with four hits to jumpstart Pittsburgh's offense in an 8-1 win over the Astros to avoid a sweep.
* At Chicago, Kyle Lohse (16-3) and the St. Louis Cardinals won for the sixth time in seven games, holding their lead in the NL wild-card race with a 6-3 win over the Cubs.
* At Cincinnati, Adrian Gonzalez hit two homers, powering the Los Angeles Dodgers to a 5-3 win over the Reds. The Dodgers remained three games behind St. Louis and a half-game behind Milwaukee for the second wild card.
The Reds rested several regulars a day after clinching their second NL Central title in 3 years. Manager Dusty Baker briefly visited the clubhouse after his release from a Chicago hospital, where he spent 4 days getting treatment for an irregular heartbeat.