CHICAGO (AP) — Rookie Luis Atilano pitched six strong innings to win for the second time in two major league starts and Adam Dunn hit a tiebreaking home run in the fourth Wednesday, leading the Washington Nationals to a 3-2 victory over the Chicago Cubs.

Adam Kennedy also homered for the Nationals (12-10), who hadn't been two games over .500 this late in a season since they were 81-79 on Sept. 30, 2005 — their inaugural campaign in Washington.

Atilano (2-0), who worked six quality innings in his debut against the Dodgers last week, allowed two runs on six hits — all singles — and three walks.

The 24-year-old right-hander pitched out of a one-out, bases-loaded jam in the fifth by retiring Marlon Byrd on a soft liner and Mike Fontenot on a grounder. After Fontenot's out, Atilano pumped his fist to celebrate.

Brian Bruney, Tyler Clippard and Matt Capps each pitched one scoreless inning of relief. Capps earned his major league-leading 10th save in 10 attempts. Washington's bullpen has a 0.77 ERA in its last eight games.

Ryan Dempster (2-1) lost for the first time in eight career decisions against the Nationals-Montreal Expos franchise. He allowed only four hits and one walk in eight innings but each hit factored in the scoring: the homers by Kennedy and Dunn and second-inning singles by Roger Bernadina and Wil Nieves.

It was 2-2 in the fourth when Dunn put Dempster's 3-1 pitch into the left-field bleachers. Dunn has 41 homers in 409 career at-bats against the Cubs.

Twelve of Chicago's 22 games have been decided by two runs or fewer. The Cubs are 4-8 in those games, a big reason they have a 10-12 record.

The Cubs, who stranded 11 runners, scored on Aramis Ramirez's sacrifice fly and Ryan Theriot's RBI single.

NOTES: Cubs CF Byrd lost Atilano's fifth-inning fly in the sun but still managed to make a no-look, behind-the-back catch while falling to his knees. ... Theriot is batting .487 during an eight-game hitting streak. He has had multiple hits in seven of those games. ... The Nationals are 6-2 in games caught by Nieves. ... Nationals manager Jim Riggleman said 3B Ryan Zimmerman (right hamstring soreness) could have pinch-hit if necessary and said Zimmerman should play Friday at Florida. ... Kennedy was in a 2-for-20 slump before his first homer this season.