Alex Ovechkin scored twice, Connor McMichael had four assists, and Ryan Leonard and John Carlson each had a goal and an assist for the Capitals (22-15-6), who had lost two in a row and six of eight (2-4-2). Charlie Lindgren made 41 saves.
Chris Kreider, Beckett Sennecke and Jacob Trouba scored for the Ducks (21-18-3), who have lost six straight (0-5-1) and 10 of 12 (2-8-2). Petr Mrazek allowed five goals on 24 shots before being replaced after the second period by Lukas Dostal, who made three saves.
Kreider gave the Ducks a 1-0 lead at 6:33 of the first period on a one-timer from the right circle off a pass from Olen Zellweger.
Sourdif tied it 1-1 at 15:56, taking a drop pass from McMichael and beating Mrazek with a high stick-side wrist shot from the slot.
Sourdif gave the Capitals a 2-1 lead at 18:58 when he received a pass from McMichael on the rush and scored with a high wrist shot glove side from the top of the right circle.
Leonard made it 3-1 at 5:54 of the second period when he knocked the puck in off Mrazek from behind the goal line.
Sourdif extended it to 4-1 at 7:30, starting a passing sequence by dropping the puck to Trevor van Riemsdyk and finishing it by tipping in a centering pass from Leonard.
Ovechkin pushed it to 5-1 at 8:52 on a wrist shot from the left circle.
Alex Killorn cut it to 5-2 at 12:56 when he beat Lindgren with a wrist shot from the right hash marks.
Trouba made it 5-3 at 14:12, scoring on a slap shot through traffic from the right point.
Sennecke then cut it to 5-4 at 9:22 of the third period, knocking in a loose puck from the slot.
Carlson scored into an empty net at 18:46, however, to make it 6-4. Ovechkin also scored an empty-net goal at 19:18 for the 7-4 final.
