Philadelphia, PA (Sports Network) - Raul Ibanez drove in the only run of the game, as Roy Halladay and thePhillies blanked the Nationals, 1-0, in the start of a three-game series at Citizens Bank Park.

Halladay (16-8) had runners on in each of his seven innings, scattering eight hits and three walks while fanning five to win his sixth consecutive start.

Ryan Madson and Brad Lidge each hurled an inning of relief to finish off Philadelphia's 14th shutout of the season and the club's fifth win in six games to stay in front in the National League Wild Card race and remain 2 1/2 games behind the NL East front-running Braves.

Jason Marquis (0-6) remains winless on the year after giving up the lone run on four hits and four walks in a five-inning start, though he did lower his earned-run average by nearly three runs to 11.39.

Washington went 0-for-11 with runners in scoring position and stranded 12 to fall for the third time in four games.