Pittsburgh, PA -- (Sports Network) - Jason Marquis threw seven scoreless innings and combined with two relievers on a five-hit shutout, as the Chicago Cubs completed a three-game sweep of the Pittsburgh Pirates with a 2-0 victory at PNC Park.

Ronny Cedeno and Henry Blanco knocked in runs for the Cubs, who have won five in a row and increased their lead in the NL Central to six games over Milwaukee, after St. Louis beat the Brewers later Wednesday. Chicago swept Pittsburgh for the third time this year and finished 14-4 against the cellar- dwelling Pirates for the season.

"All these teams that you play at the end of the season present a challenge," said Cubs manager Lou Piniella. "You must be ready to play and you can't take anything for granted."

Marquis (9-7) allowed five hits and struck out three without walking a batter. He improved to 3-0 in his last four starts and hasn't lost since falling to Pittsburgh on August 1.

Zach Duke (4-13) was the hard-luck loser and fell to 0-9 in 14 starts since his last victory on June 9 against Arizona. The lefty was charged with two runs on seven hits with two walks and six strikeouts in eight innings.

"Zach gave us eight solid innings and they got the two runs in the one inning," said Pirates skipper John Russell. "[Duke] did a nice job; it's unfortunate that we didn't score."

Raul Chavez had two hits for the Pirates, who have lost seven in a row and 11 of their last 13.

The Cubs finally broke the stalemate in the seventh inning. Reed Johnson led off with a bunt single, raced to third on a double to left by Mark DeRosa and scored when Cedeno was retired on a slow bouncer to third. Blanco then popped up a suicide squeeze bunt, but the ball fell just fair along the first base line and DeRosa scored to make it 2-0.

Marquis retired Pittsburgh in order in the bottom of the seventh, then left for Carlos Marmol in the eighth. Doug Mientkiewicz drew a walk to start the eighth, but Marmol got Nyjer Morgan to pop up a bunt before fanning Jack Wilson and Nate McLouth.

Kerry Wood struck out the first two batters he faced in the ninth, then got Freddy Sanchez on a grounder to short to end the game and notch his 27th save.

"Marquis threw a very good game against us and when you get to the back end of their bullpen, with Marmol and Wood, it's tough to get anything against those guys," Russell added.

After the Cubs posted victories of 12-3 and 14-9 in the first two games of the series, pitching dominated Wednesday.

Chicago stranded Alfonso Soriano after a leadoff double in the first. Soriano was picked off first following a two-out single in the third and the Cubs also made another baserunning mistake in the fourth when Ryan Theriot doubled and was thrown out at third trying to advance on a grounder to short by Aramis Ramirez. Soriano also stranded a pair of runners in the fifth when his fly ball to deep left was caught by Brandon Moss.

The Pirates stranded a runner at third in the first, then failed to score with two on and one out in the third as Wilson flied out and McLouth popped up. Sanchez tripled with two outs in the fourth, but was left at third when Andy LaRoche flied to center.

Game Notes

The Cubs finished with their most victories against Pittsburgh since a 15-7 mark in 1954. It also marked the most wins for the Cubs against one opponent in a single season since posting 15 against St. Louis in 1978...The Pirates purchased the contract of pitcher Jesse Chavez from Triple-A Indianapolis before the game and optioned pitcher Craig Hansen to the minor league club while also opening a spot on the 40-man roster by transferring pitcher Phil Dumatrait to the 60-day disabled list.