When Rick Nash scored the Rangers’ third goal — the eventual game-winner in their 4-2 defeat of the Washington Capitals — I noticed that the zone entry on that play was far from crisp. Nash lost handle of the puck around the left faceoff circle on the Caps’ side of neutral zone and then had to reach back to gather it back. He pushed the puck towards the blue line, and it slowly rolled as Nash was entering the offensive zone. He then fired a shot using John Carlson as a screen and beat Braden Holtby — the goal Peter described as a “back-breaker” in his recap.
Further review clearly shows: Nash was offsides on the play. It should’ve been blown dead.

From the NHL rulebook:
A player is on-side when either of his skates are in contact with, or on his own side of the line, at the instant the puck completely crosses the leading edge of the blueline regardless of the position of his stick. However, a player actually controlling the puck who shall cross the line ahead of the puck shall not be considered “off-side,” provided he had possession and control of the puck prior to his skates crossing the blue line.
There may be some confusion about what the “leading edge” is. The leading edge is the farthest edge of the blueline from the zone that the puck exits. When the puck is cleared from the defensive zone to the neutral, the blueline is part of it, and the puck must fully cross the blueline to be considered cleared. However, when a player enters the zone, the blueline is part of the neutral zone. The puck must fully enter the zone and no part of the puck may be on the blue paint when a player is already in the zone with both of his skates.
Thanks to bill_brister70 for this graphic.
“Figure A” is Nash’s situation. When the puck is partially or fully on the blueline, you cannot enter the zone.
The words “actually controlling of the puck” usually refer to the player handling the puck, not just pushing it towards the zone.
Therefore, the call on the ice should’ve been offside against the Rangers.

