Tom Wilson also scored for Washington, which won for just the second time in five games. The Capitals are in the midst of a tough stretch, playing 11 times in the past 18 days.
Mike Hoffman and Erik Karlsson scored for Ottawa, which outshot Washington 30-22. The Capitals took all three games against the Senators this season.
Washington's Alex Ovechkin was held scoreless with just one shot on goal. He remains three goals away from reaching 600 for his career.
The Capitals were hampered by seven penalties and were forced to play three-on-five twice in the opening two periods. Ottawa finished 1-for-7 on the man advantage.
Senators forward Mark Stone had an assist, extending his point streak to six games.
The Capitals tried to slow the game with a two-goal lead in the third period, but the strategy backfired as a goal by Karlsson cut the margin to 3-2 with 16:46 remaining. However, Washington settled down and held on for the win.
The Capitals took a disheartening 5-1 loss to the Columbus Blue Jackets on Monday. In that game, goalie Braden Holtby was pulled after the first period and replaced by Philipp Grubauer, who did not allow a goal.
Grubauer got the start against Ottawa and was stellar again, finishing with 28 saves. He has won his past four starts.
Mike Condon made 19 saves for Ottawa.
Wilson got the best of Ottawa's Mark Borowiecki in a fight just three minutes into the opening period that set the physical tone. Washington took a 1-0 lead just seconds after killing a power play on a goal by Kuznetsov with 4:44 left in the opening period.
The Capitals pulled ahead 2-0 just 43 seconds into the second period on a goal by Wilson. The Senators got on the board on a long-distance shot by Hoffman with 13:35 remaining in the middle period.
After the Capitals killed another two-player penalty, Kuznetsov provided a 3-1 lead when he scored with just 12 seconds left in the second period.
The Capitals recalled forward Travis Boyd from the Hershey Bears of the American Hockey League prior to the game, but he did not play.
--Field Level Media
Ottawa | Washington | |
Erik Karlsson 2 | Points | Evgeny Kuznetsov 2 |
Erik Karlsson 1 | Goals | Evgeny Kuznetsov 2 |
Erik Karlsson 1 | Assists | Matt Niskanen 2 |
Mike Hoffman 1 | Power Play Goals | N/A |
N/A | Short Handed Goals | N/A |
Mike Condon .864 | Save Percentage | Philipp Grubauer .933 |
Mike Condon 19 | Saves | Philipp Grubauer 28 |
Team | Shots | Goals | Power Play | Penalty Kill | Penalty Mins | Face Offs Won |
Ottawa | 30 | 2 | 1-7 | 2-2 | 9 | 24 |
Washington | 22 | 3 | 0-2 | 6-7 | 19 | 36 |