Abbott, 26, has seven goals, 17 assists and is a minus-3 in 46 games for the Toronto Marlies of the AHL this season. He has played in one career NHL game. He is set to become an unrestricted free agent after the season. He will report to the Blackhawks' AHL affiliate, the Rockford IceHogs.
Brennan, 25, was acquired by the Blackhawks along with other prospects from the New York Islanders in exchange for Nick Leddy on Oct. 4, 2014. Brennan led the IceHogs with 36 points, which included nine goals and 27 assists in 54 games. He has four goals and seven assists in 40 career NHL games. He is set to become a restricted free agent after the season.