Troy Brouwer, Jonathan Huberdeau and Frank Vatrano also scored for the Panthers, and Aleksander Barkov had three assists. Barkov has 94 points this season, tying Pavel Bure for the franchise record set in 1999-00.
Roberto Luongo made 27 saves as the Panthers won their third straight game.
Jakub Vrana, Nicklas Backstrom and Evgeny Kuznetsov scored for Washington, and Pheonix Copley stopped 29 shots in his first start since March 19. T.J. Oshie had two assists and Alex Ovechkin added an assist.
The Capitals lost for the first time in five games and missed a chance to clinch the Metropolitan Division title. Washington leads the New York Islanders, who lost to Toronto, by three points with two games to play.
After trailing 4-0, the Capitals scored three goals in the third period.
Kuznetsov redirected a shot from the point by John Carlson past Luongo to make it 4-1 with 9:05 left. Backstrom’s one-timer pulled the Capitals to 4-2 with 3:35 remaining. Vrana’s shot from the right side made it 4-3 with 2:21 to go.
Trocheck’s second goal, an empty-netter with 26.5 seconds left, pushed the lead to 5-3.
Huberdeau stretched the Panthers’ advantage to 2-0 with a shot from the low slot that beat Copley at 3:34 of the second.
Trocheck’s short-handed goal at 12:01 made it 3-0. Trocheck skated in on Copley and beat him between the legs.
Brouwer made it 4-0 when he put the puck behind Copley with 2:03 left in the second.
Vatrano gave the Panthers a 1-0 lead when his shot from the slot went over Copley’s glove and high into the net with 6:12 left in the first.
Capitals forward Brett Connolly played after sitting out a 6-3 win against Tampa Bay on Saturday due to illness. … Trocheck’s goal in the second was the Panthers’ second short-handed goal in two games and third this season. … The Panthers went 3-0-0 against the Capitals and swept the season series for the first time.
Capitals: Host the Montreal Canadiens on Thursday.
Panthers: Host the New York Islanders on Thursday.