 He recorded nine points and appeared in all 24 games of the playoffs while logged over 25 minutes of ice time to help the Washington Capitals claim their first Stanley Cup.Returning for his 12th season in the NHL in 2018–19, Niskanen contributed with 8 goals and 17 assists for 25 points in 80 regular season games for the Capitals.He posted 2 assists in 7 playoff games, unable to help the Capital defend the Cup in a first-round defeat to the Carolina Hurricanes.