"It's a little payback. It's funny how baseball works," shortstop Ian Desmond said. "Bryce had a good day in center, and their guy got kind of beat up a little bit."
Brewers manager Ron Roenicke felt the sun was the turning point of the game.
"It helped us yesterday on a couple of balls, and they got five runs because of it today," Roenicke said. "It would've been a good game; if that ball's caught, it's still a 2-1 game. We gave them the run in the first, but it would've been a good ballgame."
After Harper drew a walk to put runners on first and second, Ryan Zimmerman hit an 0-1 pitch for a three-run homer over the center-field wall to make it a 7-1 game. Zimmerman finished with four RBIs on the afternoon.
"Estrada finally made a mistake on the home run, but the at-bats before that, he wasn't making many mistakes," Zimmerman said. "You have to give him some credit the first couple of times through. We just stuck with our plan and he finally made a few mistakes."
The following inning, Estrada was out in favor of reliever Kameron Loe, who allowed a two-run double to Kurt Suzuki.
Washington added three more runs in the eighth inning against left-hander Manny Parra. Zimmerman highlighted the scoring with an RBI single.
The 12 runs were more than enough for right-hander Jordan Zimmermann, who won his 12th game by pitching 6 2/3 innings and allowing one run on four hits. The run scored in the second inning, when Corey Hart led off the inning with a home run, which landed over the right-field wall.
Zimmermann threw almost nothing but fastballs the first few innings. He didn't want to reveal all of his arsenal early in the game.
"I was throwing the fastball and getting ahead, and when I do that, I feel like I can control the game and do what I want, when I want, and I was able to do that," Zimmermann said. "I'm glad I'm having a few good ones here as the regular season is coming to a close. I feel if I stay on my fastball, I'll be able to throw what I want. I'm not going to be walking guys."
Zimmermann had two hits -- including an RBI single to ignite the six-run fourth.
"That was a huge hit to get us going a little bit. He is a good athlete. All of our pitchers have hit very well [this year]," Zimmerman said.
Left-hander Sean Burnett and righties Tyler Clippard and Drew Storen finished off Milwaukee the rest of the way.
The Nationals go on the road to play the Phillies starting Tuesday night. The Nationals have a chance to win the NL East title in Philly, which the Nats would welcome, for the Phillies have clinched three division titles against Washington.
Once they clinch, the Nationals hope to rest some of their starters for the rest of the regular season.
"We have to worry about tomorrow's game," Desmond said. "The rest of it will take care of itself. We have done that all year long, and we have done a great job of it. We have to keep our focus one day at a time.
"It's never easy when we go in there. This whole division, we all play each other pretty tough. We'll see what happens. We have to play tomorrow hard and see how it goes."