"It's not our first time we've lost during the [recent surge]," Braun said. "So we still feel good about where we're at. Obviously the season's winding down, we can't afford to have many more of these."
While Peralta surrendered three runs on five hits and four walks over his 2 2/3 innings, Nats left-hander Gio Gonzalez was sharp in what became his 20th win of the season. Gonzalez lasted seven innings, allowing two runs (neither earned) on three hits.
Peralta escaped the first two innings despite allowing four runners on base. But in the third, the 23-year-old right-hander surrendered back-to-back doubles to Jayson Werth and Bryce Harper for the Nats' first run. Two batters later, Adam LaRoche added a double of his own to score Harper and bring the score to 3-0. After two walks, a single and a throwing error by shortstop Jean Segura, Peralta loaded the bases before he was pulled for Hernandez.
Both manager Ron Roenicke and Peralta mentioned some difficulty the right-hander had getting adjusted to a steeper Nationals Park mound, though Peralta refused to use it as an excuse.
"That's not the thing," Peralta said. "The thing is I wasn't locating my pitches today."
Hernandez, who was a Montreal Expo from 2003-05 and a National in 2006 and 2009-11, escaped the third by getting Kurt Suzuki to fly out to left. But after the Brewers went down in order in the top of the fourth, the 37-year-old right-hander unraveled. With one out, Werth singled and Harper walked. A wild pitch advanced the runners to second and third before Ryan Zimmerman ripped a 2-1 sinker over the left-field wall for a 6-0 lead.
Hernandez allowed two more singles, and then Ian Desmond launched a three-run blast of his own, boosting the score to 9-0 and chasing Hernandez from the game. Right-hander Josh Stinson allowed one walk before ending the inning. Corey Hart, still working his way back from a left arch injury, also exited the game with Hernandez after an 0-for-2 day at the plate.
"It happened in a hurry," Roenicke said of Hernandez's downfall. "He did a nice job to get the out coming in, and then a quick couple of walks, a base hit and the first homer. I looked at the pitch and it looked like it was up and in OK. Zimmerman just got inside the ball, he hit it well. Then the next thing in the same [inning], two quick hits and I don't know what the pitch to Desmond was, but he hit it out."
The Brewers scored two runs in the sixth after Norichika Aoki extended his hitting streak to 12 games with a ground-rule double to straightaway center. After Harper mishandled a tough fly ball from Rickie Weeks -- ruled an error -- that put runners on second and third, Braun grounded out to shortstop to score Aoki while Aramis Ramirez knocked a sacrifice fly to right field to bring Weeks in.
Braun, nursing a groin injury from Friday night, exited after the inning. He finished 1-for-3 with a single in the first. Roenicke said both Braun and Hart are fine, and he expects Hart to play his first game against a right-hander since returning from the DL on Sunday.
"The game was at a place where if I keep them in there and they get worse, I'm not feeling too good about it," Roenicke said."
Rookie right-hander Tyler Thornburg made his second appearance since his callup from Triple-A Nashville in the sixth and served up a leadoff home run to LaRoche.
Taylor Green hit a two-run homer in the ninth to close the Brewers' scoring.
With two games left in Washington, the Brewers will attempt to avoid dropping a series for the first time since a three-game sweep at the hands of the Rockies from Aug. 13-15.
"I don't feel like we have to win every single game the rest of the season," Roenicke said. "I don't feel that. But I tell you what, we better win most of them, or all almost all of them. Even if we get help, we need to really play well."