Capuano pitched into the ninth, striking out a season-high nine, and Geoff Jenkins hit a homer in the 3-0 win.
The pitch that handcuffed the Nationals is one manager Ned Yost called the "Funky McNasty" in a bullpen session this weekend. Yost was monitoring Capuano closely because the left-hander left his last start early with a right calf contusion.
"He was in the background watching and doing a little commentary while we were throwing," Capuano said. "I threw one pitch which he called the 'Funky McNasty.' It was a changeup or something."
That changeup neutralized the Nationals (9-23), who have lost six in a row for the second time this year.
Capuano (5-0) pitched eight-plus innings, allowing seven hits and walking none, and the Brewers improved to 7-0 in his starts this season. He allowed just one runner past second base in the first eight innings.
Capuano showed no ill effects in his first start after taking a grounder off his leg against the Cardinals on Wednesday. He pitched three scoreless innings in that game.
Capuano said the short outing against St. Louis might have been a blessing because his shoulder was feeling tired. He saw it as a chance to rest his arm.
"I felt stronger," said Capuano, who threw 74 of his 98 pitches for strikes.
"He's tough," Washington manager Manny Acta said. "He really kept everybody off balance. He was able to spot his pitches and work guys in and out. That changeup was always on the back of these guys' minds. He did an outstanding job. Despite our struggles, you can't take anything away from him."
The victory pushed the surging Brewers to 22-10, 5½ games up on the idle Chicago Cubs in the NL Central. They were last 12 games over .500 when they finished the 1992 season 92-70.
The Brewers scored all of their runs in the third inning. Johnny Estrada and Kevin Mench singled with one out to bring up Jenkins, who had not started this season against a lefty. After taking the first pitch up and in, he sent a slider into the concourse in right center for a 3-0 lead.
It was Jenkins' sixth homer of the year and his first against a left-hander.
Jenkins came in hitting .133 in just 15 at-bats against left-handers this season. In 2006, Jenkins hit .133 with two home runs and seven RBI in 98 at-bats against left-handed pitching, one reason he is in a platoon role with Mench this year. Corey Hart is battling a sore wrist, which opened the door for Jenkins to start Monday.
"It feels great, obviously, to get in there and get a chance to make something happen," Jenkins said. "Luckily we didn't need anymore. 'Cap' did such a great job tonight on the mound we didn't need too much."
Bill Hall had three singles for the Brewers.
"It seems like there is somebody new every night doing something good, and that is the mark of a good team," Jenkins said.
Matt Chico (2-4) pitched well, giving up eight hits and three runs in seven innings. He struck out five and walked one in his longest outing of the season.
"I just went out there and was more relaxed," he said.
Austin Kearns had three hits for the Nationals.
The Nationals got some good injury news Monday, as shortstop Cristian Guzman and center fielder Nook Logan were in the lineup a day after being activated from the disabled list. Guzman had a strained left hamstring, while Logan had a strained left foot. Both went out on opening day.
"We're struggling right now," Acta said. "We're going to grind it out and keep working. We're going to get out of it."
- Capuano is the third pitcher in Brewers history to win his first five decisions as a starter, joining Bill Wegman (6-0 in 1994) and Chuck Porter (5-0 in 1984).
- The Nationals are expected to purchase the contract of RHP Jason Simontacchi, who will start against the Brewers on Tuesday. A corresponding roster move will be announced.
- Nationals 1B Dmitri Young was back in the starting lineup after being given the day off Sunday with a sore foot.
- Following the three games against the Nationals, the Brewers begin a stretch of 13 road games in their next 16 contests.