WASHINGTON -- Carlos Zambrano made up for some early wildness with another big hit at the plate.

Zambrano worked five effective innings after a shaky start and hit a key two-run double, leading the Chicago Cubs to a 3-1 win over the Washington Nationals on Friday.

"In the National League, you have to be able to pitch and you have to be able to contribute to your own cause," Zambrano said.

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Zambrano (6-4) gave up an unearned run and four singles to win his second consecutive start after going 0-2 in his previous six outings. He struck out four and walked four in a 113-pitch effort as the Cubs won for the fourth time in five games.

By going 1 for 2, Zambrano raised his season batting average to .238 (10 for 42) with seven RBI -- lofty numbers for a position in the batting order usually considered an automatic out. He hit his third homer of the season to help the Cubs beat the Cardinals 7-3 in the opener of a day-night doubleheader Sunday.

"My job is to pitch, and sometimes I get lucky and get a base hit," Zambrano said.

Washington fell to 0-2 under interim manager Jim Riggleman, who took over when Manny Acta was fired Monday. Nyjer Morgan had three hits for the Nationals, who have lost eight of nine to lower their major league-worst record to 26-63.

"The final score is the only thing that matters and we have to find a way to get those runs in," said Riggleman, whose club stranded seven men in the first four innings and nine for the game.

Aaron Heilman, Sean Marshall, Carlos Marmol and Kevin Gregg combined to pitch four innings of two-hit ball after Zambrano departed, with Gregg earning his 17th save in 20 opportunities. Aramis Ramirez homered for the Cubs.

Zambrano labored through a 40-pitch first inning and the right-hander's control problems put him in a 1-0 hole. The Nationals loaded the bases on a pair of walks and an error before Willie Harris walked with two out to force in a run.

"In the first inning, I was a little shaky," Zambrano said. "My back was also a little tight today, but nothing to worry about. After that, I was able to come back and do my job."

Second baseman Mike Fontenot's sprawling, backhanded grab of Josh Bard's grounder up the middle, followed by a no-look flip to shortstop Ryan Theriot for an inning-ending forceout, prevented further damage in the first.

"That was a tough play that Fontenot made, a really nice play," manager Lou Piniella said. "It got us out of the first inning, and from then on Zambrano basically got better as the game progressed."

Zambrano quickly atoned for his wildness, coming up with a big hit in the second. Milton Bradley drew a leadoff walk and Fontenot doubled with one out to put runners on second and third. After Koyie Hill grounded out, Zambrano doubled down the right-field line to give the Cubs a 2-1 lead.

"I try to treat [pitchers] like a regular hitter and try to pitch them the same way instead of just grooving fastballs in there," Nationals starter Craig Stammen said. "I left a curveball that didn't break as much as I expected it to and [Zambrano] put a good swing on it."

Ramirez hit a two-out drive off Stammen into the seats in left in the third. It was his fifth homer.

Stammen (2-5), pushed up a day after left-hander Scott Olsen was scratched from Friday's start with back muscle tightness, allowed three runs and six hits in six innings.

Notes

• Washington SS Cristian Guzman (bunions) was scratched and replaced by Alberto Gonzalez.
• Chicago played without OF Alfonso Soriano, who was nursing a swollen pinkie finger on his right hand. Soriano was injured diving back to first when he was tagged out after making a wide turn on a single Thursday night.
• Chicago LHP Ted Lilly won't start Saturday because of a sore left knee. RHP Randy Wells will be moved up instead of starting Sunday.
• Cubs LF Micah Hoffpauir made a nice grab to end the third, pushing past a frozen-in-place ballgirl, diving into the stands and outmuscling a fan for Harris' foul pop. The next time a foul pop came her way, the ballgirl jumped into the stands to avoid any contact.
• Olsen's back hasn't improved and he won't be able to start Monday either, Riggleman said. Olsen was examined by a team doctor Friday, but may see another physician Saturday.