The honour goes to the NHL's top rookie. The winner will be announced during the 2013 Stanley Cup final.
Gallagher ranked second among NHL rookies this past season with 15 goals. He had 28 points in 44 games and finished in the top five among league freshmen in shots on goal (117), plus-minus (plus-10) and game-winning goals (three).
The 21-year-old forward was selected by the Canadiens in the fifth round of the 2010 NHL Entry Draft.
Huberdeau, selected by the Panthers with the third overall pick in 2011, had 31 points (14-17) in 48 games. Saad, picked by the Blackhawks in the second round of the 2011 draft, had 27 points (10-17) in 46 games.
Members of the Professional Hockey Writers' Association submitted ballots for the Calder Trophy at the conclusion of the regular season. The top three vote-getters were designated as finalists.
The NHL will announce the finalists for the James Norris Memorial Trophy on Tuesday. The honour goes to the top defenceman.