The 14-year veteran goaltender is in his first season with the Capitals after spending the previous four with Florida. He has 46 shutouts in 662 career games. His single-season high has been seven, established two years ago.
Washington extended Pittsburgh's losing streak to six games, a slump that has seen the Penguins tumble 12 points behind the division-leading New York Rangers.
The game's only goal came from Jason Chimera with 4:35 to go in the opening period. It was his 14th of the season.
Marc-Andre Fleury made 20 saves in taking the loss. The Penguins have scored no more than one goal in any of their last five games.