Kuznetsov scored his 18th and 19th goals of the season and the Capitals killed six of seven penalties en route to a 3-2 victory over the struggling Senators.
''I thought the PK was the start. I thought our resiliency was a start,'' Washington coach Barry Trotz said. ''And we sort of had each others' back a little bit. We took some penalties, warranted or not, and we had to battle through with it.''
Tom Wilson also scored for Washington, which completed a 3-0 season sweep of Ottawa to move back into first place in the Metropolitan Division by one point over Philadelphia.
Capitals No. 2 goalie Philipp Grubauer made 28 saves in his 18th start and fourth straight win. Matt Niskanen assisted on both of Kuznetsov's goals, each coming less than a minute after one of Ottawa's failed power plays.
''Pretty special night by Kuzy,'' Wilson said. ''He's really feeling it as of late. It's pretty fun to watch when he turns it on.''
Kuznetsov has three goals and three assists over his last three games.
The Capitals entered with the NHL's 19th-ranked penalty kill unit, but got the better of the Senators' 27th-ranked power play. A day before, the same unit allowed two goals in a 5-1 road loss at Columbus.
''It's been a little bit up and down lately,'' Grubauer said of the team's overall performance. ''You've got to find a way to make sure the next one is as good as this one.''
Erik Karlsson had a goal and an assist a day after Ottawa elected not to deal the All-Star defenseman at the NHL trade deadline
Mike Hoffman added his 18th goal on a second-period power play for the Senators, who have lost five straight overall and 22 of their last 25 on the road.
Ottawa's man-advantage struggles included failing to score during two 5-on-3 stretches that totaled 2:20, though Hoffman's goal came seconds after the first one ended. The Senators' power-play unit didn't apply much pressure after Washington's last two penalties.
''A lot of around and around and around, and no pucks on net,'' coach Guy Boucher lamented. ''No pucks on net, 100 percent sure of not scoring.''
Kuznetsov put Washington up 1-0 late in the first period on a breakout only 12 seconds after the Capitals completed their first penalty kill, easily one-timing T.J. Oshie's cross-ice feed past goaltender Mike Condon.
Kuznetsov struck again moments before the second period expired, making it 3-1 when he beat Condon on a slick wraparound.
Karlsson snuck in a shot from a tight angle behind Grubauer early in the third to cut Ottawa's deficit to one. But the Capitals killed two more penalties in the final period to preserve their win.
''The percentage and the kill on the year and the rank in the league, it doesn't matter,'' Wilson said. ''It comes down to big kills late in the game, and we got the job done tonight.''
NOTES: Senators D Mark Borowiecki strained his neck in the first period and did not return. . Ottawa D Chris Wideman (hamstring) rejoined the team for practice on Monday. He hasn't played since Nov. 16. . Grubauer started after playing the final two periods of Washington's 5-1 loss Monday night. . Swedish Ambassador to the United States Karin Olofsdotter was in attendance.
Senators: Visit the Vegas Golden Knights on Friday.
Capitals: Host the Toronto Maple Leafs in an outdoor game Saturday at U.S. Navy Marine Corps Stadium in Annapolis, Maryland.
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