Senators overwhelm Caps 5-2
Karlsson finished with a goal and two assists to set a new franchise record for assists by a defenseman in a season with 47.
The 21-year-old now has seven points in his last two games. His 60 points on the season give him a 20-point lead on Florida's Brian Campbell for the NHL lead in scoring by a defenseman.
Michalek added two goals and an assist, while Chris Phillips, with his fourth goal in six games, also scored for Ottawa. Craig Anderson made 33 saves.
Nick Foligno scored into an empty net for Ottawa.
Tomas Vokoun allowed four goals on 11 shots before being replaced midway through the second period by Michal Neuvirth. He finished with 14 saves. Washington has been outscored 12-3 on its losing streak, and has lost six of its last seven.
Ottawa jumped out to a 2-0 lead on the back of Karlsson.
The smooth-skating defenseman opened the scoring at the nine-minute mark of the first with a shot that beat Vokoun through the legs. Karlsson then fed Michalek five minutes later and he made a great move around Dennis Wideman before beating Vokoun from in close.
Michalek added his second of the night on a deflection off Karlsson's point shot on the power play early in the second. Michalek's 27th goal of the season set a new career high.
Vokoun's night came to an end after Phillips made it 4-0 on the power play midway through the period.
Despite being in a huge hole, Washington showed some jump in the third period to cut the lead to 4-2.
Carlson finally got the Capitals on the board with a power-play goal early in the period and Perreault made it 4-2 as the puck went off his face and past Anderson.
This was the final regular season meeting between the two teams. Washington took the first three.
NOTES: Ottawa has outscored its opponents 21-4 in its last four games. ... With an assist on Karlsson's goal, Jason Spezza extended his point streak (seven goals, nine assists) to seven games. ... The Senators were without C Peter Regin (shoulder, out for season), C Jesse Winchester (concussion, indefinitely). D Matt Carkner and C Zenon Konopka were healthy scratches. ... In addition to Ovechkin, the Capitals were without D Tom Poti (strained groin, indefinitely), C Nicklas Backstrom (concussion, indefinitely). Ds John Erskine and Roman Hamrlik were healthy scratches.