Zimmermann allowed one run in seven innings, a line that is becoming a habit for him this year, and Washington scored a pair of runs in the eighth inning to pull out a 3-2 victory against the Houston Astros.
The Nationals improved to 10-3 -- they became the first team in the majors to reach 10 wins this season. Texas earned its 10th victory later in the evening.
"A win's a win, no matter how we get it," said Zimmermann, who allowed four hits, struck out three and did not walk a batter. "We're getting in the late innings the last couple games, which makes it extra exciting."
This was the seventh one-run game for the Nationals this season, and they have a 5-2 record in those close contests.
"We understand we're not going to win every one-run game," third baseman Ryan Zimmerman said. "A couple five- or six-run wins would be nice every now and again too."
There was hardly a mention of reaching 10 wins in the Nationals clubhouse, even though the team is off to its best start since moving to Washington from Montreal in 2005.
"I think the best thing we have going is we understand it's early, we're not really taking this over the top," Zimmerman said. "We understand we're going to have some times where we don't play this well, and we're going to have some more times where we do play this well. For a young team, I think we're very mature."
Houston took a 2-1 lead in the top of the eighth. Jason Castro led off with a double and Zimmerman held him there with a pair of highlight defensive plays -- a sliding catch in foul territory of a popped-up bunt and a diving catch on a sharp line drive -- before Jordan Schafer's RBI single that just hopped past the glove of the diving LaRoche at first.
For much of the game, it appeared the two teams were headed for a second straight 1-0 game, as the starters held both offenses in check. Zimmermann and Houston's Lucas Harrell both pitched into the seventh inning, allowing a run apiece.
It is becoming a habitual line for Zimmermann, who is still waiting for his first win despite allowing one earned run over seven innings in each of his three starts this season. In his 21 innings pitched, the Nationals have scored a total of two runs, including one on Roger Bernadina's two-out double in the bottom of the seventh against Houston.
"You can sit here and analyze the numbers all you want, but the fact of the matter is we've got to score him runs," Werth said.
Houston lost its fourth in a row and seven in eight games. Four of the Astros' last five losses have been by one run.
"The ball isn't falling our way," Castro said. "We've had a couple of bad breaks and we just keep playing."
"For us to win that game right there, that's a testament to this team and how hard we play and our ability to come back," Werth said. "We believe in ourselves. We're a good club. As the season goes on, we'll continue to prove it."
Nationals RHP Chien-Ming Wang (left hamstring) threw 35 pitches in a simulated game in Viera, Fla. Washington manager Davey Johnson said Wang would pitch a minor league rehab assignment in five days. ... Johnson said RHP Brad Lidge had suffered from vertigo the past four days, including Tuesday when he earned his second save, but was feeling better Wednesday. ... Houston LF Travis Buck left the game in the middle of the fourth with a mild left hamstring strain after getting an RBI on a groundout. ... Houston RHP Bud Norris (0-0, 4.15 ERA) will face Nationals RHP Edwin Jackson (1-0, 2.57 ERA) in the final game of the four-game series Thursday.