HOUSTON -- As Kaz Matsui hit ball after ball into the stands during a recent batting practice, Astros manager Cecil Cooper teased him about being a home run hitter.

Matsui protested, insisting that he was no home run hitter.

He showed that he can be one Sunday, knocking a three-run shot to lead the Houston Astros to a 5-0 win over the Washington Nationals.

"The was a good thing that it happened," he said through a translator. "I'm not a home a run hitter. I just try to get on base. I've only hit three home runs, but the home run [today] was big."

Matsui's shot into the first row of the stands in right field near the bullpen came in the seventh inning and gave Houston a 4-0 lead. The win gave the Astros a 3-1 series victory over the last-place Nationals. The Astros leave Houston at .500 heading into the All-Star break.

The Astros received another solid start from Brian Moehler (6-5), who allowed seven hits in 6 1/3 innings to win for the fourth time in five decisions. Closer Jose Valverde recorded the last four outs for his eighth save of the season and the 150th of his career.

"Terrific, terrific job by Mr. Brian Moehler today," Cooper said. "We definitely needed it today, and he stepped up in a big way. We were a little short-handed. We only had two or three guys out there in the bullpen and Brian stepped up really huge for us."

Houston added a run in the eighth inning when Lance Berkman scored on a balk by Tyler Clippard, who looked to have lost his balance and almost fell off the mound.

"He caught his spikes on the dirt," Nationals manager Manny Acta said. "But all he had to do was release the ball and let it roll and it wouldn't have been a balk. But he's just a kid and he didn't know."

Geoff Blum was hit by a pitch in the seventh before Hunter Pence singled. Ivan Rodriguez struck out before Matsui's homer. Nationals starter Jordan Zimmermann (3-4) walked reliever Alberto Arias before he was replaced by Joe Beimel, who finally got out of the inning.

A day after getting their most runs (13) and hits (21) of the season, the Nationals recorded 11 hits but couldn't convert, leaving 13 men on base.

"We had a lot of hits, we just didn't have hits in the clutch situations," said Washington's Wil Nieves, who finished with a career-high four hits. "We had a couple of opportunities with runners in scoring position but we just couldn't do the job."

Nieves singled in the seventh before advancing to second on a sacrifice bunt by Zimmermann. Moehler was replaced by Arias, who allowed a single by Nyjer Morgan. Nick Johnson walked to load the bases for the second inning in a row, but the Nationals came away empty again after Ryan Zimmerman popped out and Adam Dunn grounded out.

Houston was helped on that play by shifting the defense to the right to deal with the left-handed Dunn. The shift left Miguel Tejada behind second base and in perfect position to grab Dunn's grounder and get it to Berkman at first for the out.

Johnson doubled to open the sixth inning before Moehler yielded back-to-back walks with one out to load the bases. He got out of the jam by retiring Alberto Gonzalez and Anderson Hernandez to end the inning.

Tejada's single in the first inning scored Michael Bourn and gave Houston a 1-0 lead. Bourn had reached and advanced to second when Gonzalez overthrew first base.

Carlos Lee got a double in the fourth inning on a fly ball to left-center field. The Astros argued that it hit above the yellow line on the wall and should be a home run and the officials reviewed the call. Replays showed it hit below the line and the call stood.

Zimmermann yielded five hits and four runs with six strikeouts in 6 1/3 innings.

Notes

Astros RHP Doug Brocail, on the disabled list with a left hamstring injury, will throw a bullpen session on Tuesday and is scheduled to throw a simulated game Friday. He threw a bullpen session Sunday and said he is feeling great. ... Houston optioned RHP Felipe Paulino to Triple-A Round Rock after the game. The Astros will likely bring LHP Wesley Wright up from Round Rock on Thursday to fill the roster spot. ... Washington will option LHP Ross Detwiler to Triple-A Syracuse and will likely bring up RHP Garrett Mock.