Winning pitcher CC Sabathia (6-4) gave up six hits, including a three-run homer by Anderson Hernandez, in 7 2/3 innings.
Mariano Rivera pitched a scoreless ninth for his 15th save of the season.
Yankees shortstop Derek Jeter left Tuesday's game before the bottom of the eighth with left ankle stiffness.
Nationals starter Shairon Martis allowed only two runs -- one earned -- in six innings. Ron Villone (3-4) took the loss after giving up two runs in the seventh.
Copyright 2009 by United Press International.