PITTSBURGH (AP) -- Washington won 4-1 at Pittsburgh on Monday to spoil Mike Sullivan's coaching debut for the Penguins.
Sullivan took over the position following the firing of Mike Johnston on Saturday, but saw his team lose heavily against a Capitals outfit led by two goals and an assist from T.J. Oshie.
Among other results, Ottawa beat Los Angeles on the back of a four-goal second period, and Buffalo won at Detroit for the first time in nine years.
Washington's Nicklas Backstrom had a goal and two assists while John Carlson also netted for the Capitals, who moved 11 points above their Metropolitan Division rival.
Evgeni Malkin scored his team-leading 14th goal for the Penguins.
Ottawa's Mike Hoffman had two goals and an assist to lead the Senators over Los Angeles 5-3.
Kyle Turris, Erik Karlsson and Mika Zibanejad also scored for the Senators.
Jamie McBain, Tyler Toffoli and Jake Muzzin netted for Los Angeles, who missed a chance to build on their 10-point lead in the Pacific Division.
Buffalo's Ryan O'Reilly and Johan Larsson scored 61 seconds apart late in the third period to give the Sabres a rare win at Detroit, beating the Red Wings 2-1.
O'Reilly tied it 1-1 at 15:46 when his deflected shot beat goalie Petr Mrazek between the legs. Larsson scored the go-ahead goal with 3:13 remaining; his first goal in 30 games.
Brad Richards scored for the Red Wings, whose run of games earning at least a point ended at 13.
Edmonton's Andrej Sekera scored 41 seconds into overtime to lift the Oilers over Boston 3-2 for their sixth straight victory.
Tampa Bay's Brian Boyle scored a short-handed goal in the third period to help the Lightning beat Columbus 2-1.