"I felt fine, but the stuff wasn't where it was supposed to be," Zimmerman said. "I just wasn't locating. Everything was over the middle and I was falling behind guys."
It was only the second start this season Zimmermann had given up as many as six runs, and it was his second-shortest outing of 2015.
Despite the outcome, returning to Miller Park is always special for Zimmerman. Numerous friends and family always make the trip to tailgate before his starts in Milwaukee.
"It's awesome," Zimmermann said. "It's only three hours from home, so it's good for everyone to come down and be able to see me. They all enjoy it and have a good time with the tailgate.
"I wish we had a better outing, but I'm glad they could come down and watch."
Zimmermann's underwhelming performance has become a trend among Nats starters recently. Friday's loss marked their eighth defeat over the past 10 games. In those eight losses, the team has allowed an average of 5.87 runs per game.
The struggles from the rotation have surprised Nats manager Matt Williams, especially for a team built off starting pitching.
"All of our starters will be just fine," Williams said. "They're going through a rough patch right now, but they'll come out of it. We'll get through it."
"We have to attack," Zimmermann added. "Our stuff is good enough to go right after guys. As long as we aren't nibbling and trying to be too perfect, that's when we get in trouble."
Brandon Curry is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.