Ice Hockey in 2019: Offside — Section 917: Offside

The objective of ice hockey is to score more goals than the opposition by shooting the puck across the opponent's goal line and into a net guarded by a goaltender. Each team dresses six players, three forwards (left wing, centre, right wing), two defencemen and a goaltender, though teams rotate roughly four forward lines and three defensive pairings throughout a game. A goal counts one point on the scoreboard, and unlike many sports, scoring is relatively scarce: a typical NHL game finishes around six goals combined, which magnifies the value of every shift and every mistake.

A contest is divided into three periods of twenty minutes of running clock, stopped for every whistle. Referees drop the puck at a face-off to start play, and the game flows continuously until an infraction, a goal, or the puck leaving the ice halts it. Special situations, penalties that send a player to the box, delayed calls, and empty-net gambles, shape strategy far more than the raw run of play. If the score is level after regulation, overtime and, in many competitions, a shootout decide the winner.

A player is offside if he precedes the puck across the attacking blue line; both skates must remain behind the blue line until the puck fully crosses it. If an attacker enters the zone early, a linesman blows the play dead and a face-off follows outside the zone. Since 2019 the NHL judges offside by whether a skate is in contact with or above the ice over the blue line, and coaches can challenge a goal scored on a missed offside. The rule prevents cherry-picking and forces teams to carry or dump the puck in with control.