Chicago, IL -- (Sports Network) - Willie Harris homered twice, including his first career grand slam, and drove in six runs as the Washington Nationals stunned the Cubs by coming back to down Chicago, 13-5, in the opener of a three-game series.

Aaron Boone had a pinch-hit three-run double, and Ronnie Belliard went 4-for-5 with a homer, two RBI, and scored three times for the Nationals, who have won consecutive games after dropping 12 in a row.

John Lannan (7-12) took advantage of the rare offensive outburst, getting the win despite giving up five runs on seven hits in 6 1/3 innings with three strikeouts and three walks.

Jason Marquis gave up four runs in 5 1/3 innings with three strikeouts and three walks, squandering an early 4-0 lead in a no-decision. Neal Cotts (0-2) gave up two runs in two-thirds of an inning, part of a Cubs bullpen that was ripped for nine runs on nine hits in 3 2/3 innings.

Mark DeRosa and Derrek Lee each homered for the Cubs, who have dropped two of three.

Trailing 4-0, the usually offensively challenged Nationals roared back with six runs in the sixth. Washington loaded the bases with no outs on an Emilio Bonifacio infield single and walks to Cristian Guzman and Ryan Zimmerman. Lastings Milledge flied out to left, plating Bonifacio, and Belliard lined a double to right, scoring Guzman to cut the deficit to 4-2.

That ended Marquis' day. Cotts issued a walk to Austin Kearns to load the bases and Harris made Cotts pay with his fly ball into the stands in right. The grand slam pushed the Nats in front 6-4.

Guzman's RBI single in the seventh extended Washington's lead to 7-4, but Chicago got one run back in the home half on Ryan Theriot's RBI single. The Nats scored a knockout blow in the eighth, though.

Facing Chad Gaudin, Belliard doubled to right-center to start the frame, and Harris was intentionally walked with one out. Pinch-hitter Jesus Flores singled to load the bases, and pinch-hitter Boone unloaded them with a shot that one-hopped the fence in right-center, giving Washington a 10-5 lead.

Belliard's solo homer and Harris' two-run blast, both with two outs in the ninth, padded the lead. Both came off Gaudin, who gave up six runs on six hits in two innings.

A double-steal in the first gave Chicago its first run. With Alfonso Soriano at third, Lee took off from first, and Soriano broke on the throw to second. Aramis Ramirez struck out on the pitch, but Soriano scored anyway, giving the Cubs a 1-0 lead.

Lee made it a 2-0 edge with his 18th homer of the season, to left with one out in the third, and DeRosa doubled that lead with his long, two-run homer to Waveland Avenue in the fourth.

Game Notes

DeRosa's homer was his 16th, extending his career-high for a season. His previous best was 13 with the Texas Rangers in 2006...The homers were the 11th and 12th of the season for Harris. Belliard's homer was his 11th...The four- run deficit was the largest the Nationals have overcome this season...Former Chicago Blackhawks defenseman, and Chicago native Chris Chelios sang "Take Me Out to the Ball Game," during the seventh inning stretch, along with the Stanley Cup he won as a member of the Detroit Red Wings this year.