According to the NHL Rule Book, players may be changed at any time during play, provided that they are within five feet of the bench and not in the play when the change is made. “At the discretion of the on-ice officials, should a substituting player come onto the ice before his teammate is within the five foot limit of the players’ bench (and therefore clearly causing his team to have too many players), then a bench minor penalty may be assessed. When a player is retiring from the ice surface and is within the five foot limit of his players’ bench, and his substitute is on the ice, then the retiring player shall be considered off the ice. If in the course of making a substitution, either the player entering the game or the player retiring plays the puck or who checks or makes any physical contact with an opposing player while both players involved in the substitution are on the ice, then the infraction of ‘too many men on the ice’ will be called.”
Two former NHL referees contacted by The Athletic who examined the video said that in their opinion this play wasn’t too many men. One former linesman said that while it’s close, loose line changes happen all the time and very few officials would have blown a play like this dead in overtime. He also noted that the Lightning had seven players on the ice, including two players at the bench, like MacKinnon, with the players who came on for them also engaged in the play.
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Ironically, last postseason, the Lightning’s Ondrej Palat scored a goal in Game 2 of Tampa Bay’s playoff series against the New York Islanders with seven players in the play. The officials missed it, and the goal counted.