Washington's Alex Ovechkin, who leads the NHL with 33 goals, was held scoreless on just two shots - one in regulation and none through the first two periods. He was also stopped during the shootout.
Ovechkin has at least a point in 43 of the Capitals' 54 games. But he failed to get one Saturday in Pittsburgh, and this marked the first time this season he did not register a point in consecutive games.
Olie Kolzig had 31 saves for the Capitals and was flawless in the shootout, stopping Miroslav Satan, Viktor Kozlov and Jason Blake. Washington was winless in five shootouts before Sunday.
Mike Sillinger scored the lone goal for the Islanders, and Rick DiPietro stopped 30 shots.
In the shootout, Semen went first. He went straight at DiPietro, deked right and stuffed a backhander into the net. That turned out to be the game-winner for the Capitals, who had lost eight of 10.
DiPietro hit the ice hard after being upended in the net by a sliding Ovechkin with 12:09 left in regulation, but remained in goal to the finish.
Minutes later, Ovechkin was called for interference. Shortly after he emerged from the penalty box he took his first shot on goal, with 9:17 to go.
Matt Pettinger scored a first-period goal for the Capitals, who went 0-for-4 on the power play and yielded a short-handed goal to Mike Sillinger. New York is 14-for-14 on the penalty kill over the last three games.