With the Nationals ahead, 1-0 after a Jayson Werth home run, Johnson sent Clippard out for the 8th inning after the righty had struck out Nick Hundley to leave the bases loaded in the 7th. Clippard walked Orlando Hudson with one man out before Cameron Maybin reached on a bunted base hit and Mark Kotsay doubled into the right-center field gap to score both runners.
Huston Street allowed a two-out single to Adam LaRoche in the top of the ninth inning before Werth grounded into a forceout to stop the Nationals' four-game winning streak.
Edwin Jackson got the start for Washington and pitched 6.2 shutout innings, allowing six hits and three walks as well as striking out six.
The Nationals continue their West Coast swing this weekend as they face the Los Angeles Dodgers.