Gardiner hasn't played since sustaining a concussion during a game Dec. 8 while playing for the Leafs' American Hockey League team, the Toronto Marlies. In 22 AHL games, he had nine goals and eight assists.
The 6-foot-2, 184-pound blueliner had 30 points in 75 games as a rookie with the Maple Leafs last season.
The move likely means defenseman Korbinian Holzer will be sent to the AHL.
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