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WASHINGTON -- Minimal offense, two errors that led to three unearned runs, a costly pickoff in the eighth inning with the potential tying run at the plate: The dawn of the Jim Riggleman era looked suspiciously like the kind of spotty play that got Manny Acta fired as manager of the Washington Nationals.

Rich Harden allowed three hits over six innings, Derrek Lee homered and the Chicago Cubs beat Washington 6-2 on Thursday night, spoiling Riggleman's debut as the Nationals' interim manager.

"Our guys played hard. I thought we played very well for seven innings and then it got away from us. ... There's really not a whole lot to feel good about," Riggleman said. "But I feel like we're going to turn this thing around."

Harden (6-6), who had won only one of his previous seven starts, improved to 4-1 on the road. He allowed an unearned run, walked none and struck out seven, including Adam Dunn three times.

"It's nice to have a couple of days off and kind of regroup," Harden said of the All-Star break. "[It] kind of helps put things behind you, put the first half behind you. There are a lot of games left. It's almost like you're starting over."

A managerial change did little to ignite the Nationals, who have dropped seven of eight and own the majors' worst record at 26-62. Riggleman, who previously managed the Cubs, San Diego and Seattle, replaced Acta on Monday after serving as his bench coach the first half of the season.

Nationals catcher Josh Bard wouldn't fault what he called "aggressive" errors and preached patience in wake of the leadership switch.

"There's positives to take out of it but at the end of the day we're not here to just get positives," Bard said. "They're paying us stinking boatloads of money to go out there and win baseball games and we've got to be better. We're not going to make this ship right in three hours."

Cubs manager Lou Piniella wasn't sure what to expect out of the Nationals in wake of Riggleman's ascension.

"You never know. You don't like to see anybody get fired. Riggleman's ... an experienced guy [but] sometimes it takes a while," Piniella said.

Lee had three hits and Ryan Theriot drove in two runs for the Cubs, who have won three of four.

"You just want to come out on a good foot, [it] really wasn't much of a break. ... We were playing pretty good when we went into it," Theriot said. "Hopefully, we can continue it."

Ryan Zimmerman hit his 15th homer for Washington, a ninth-inning solo shot off Kevin Gregg.

Chicago went up 1-0 in the third on an unearned run. Koyie Hill reached second on third baseman Zimmerman's throwing error, moved to third on Harden's sacrifice and scored on Theriot's two-out double to left.

"I think sometimes, Ryan gets caught between whether he's going to pick it up and fire or take another step and throw it on the run," Riggleman said of Zimmerman's error, his team-high 13th. "I think we saw a little bit of in-between there, and it didn't come out of his hand good."

Lee's 18th homer, a solo shot with one out in the sixth off a 3-2 fastball from John Lannan, made it 2-0.

The Nationals cut the lead in half in the bottom of the inning on an RBI groundout by Nick Johnson.

An RBI single by Reed Johnson restored the Cubs' two-run lead in the seventh and knocked Lannan from the game.

Lannan (6-7) gave up three runs -- two earned -- and seven hits over 6 2/3 innings.

Washington had the potential tying run up in the eighth after Morgan drew a two-out walk. But Carlos Marmol picked off Morgan with Johnson hitting and the Cubs added three insurance runs in the ninth.

Game notes

Washington LHP Scott Olsen has been scratched from Saturday's scheduled start because of back muscle tightness and will be replaced by RHP Craig Stammen. ... Before the game, the Nationals recalled RHP Garrett Mock from Triple-A Syracuse. Mock will start Sunday. ... The Cubs on Thursday signed LHP B.J. Ryan, who was cut July 8 by Toronto, to a minor league contract. Ryan will report to Chicago's spring training complex in Mesa, Ariz., to work out before joining Triple-A Iowa. ... Cubs manager Lou Piniella visited the White House on Thursday and he and his family had a five-minute meeting with President Barack Obama.