The Rush acquired Mercier's rights as the future considerations in a trade that sent Kenton Miller to Adirondack at the trade deadline last season.
Mercier played in all but four regular-season games with the Thunder as a rookie, tabulating 42 points (17g-25a) in 68 games, and adding four assists in 14 Kelly Cup Playoff games.
A native of Verdun, Quebec, Mercier played four seasons of college hockey with Bowling Green State University before beginning his professional career. With the Falcons, he compiled 76 points (22g-54a) in 157 career games. His best collegiate season came in his sophomore campaign, when he set his personal highs in all offensive categories with eight goals, 17 assists and 25 points in 38 games.