Brennan, 24, split the 2012-13 season between the Buffalo and Florida organizations. He had one goal in 10 games with the Sabres, and two goals and seven assists in 19 games with the Panthers. Brennan also had 14 goals and 21 assists in 36 games with Rochester of the American Hockey League.
Butler, 26, played for Nashville and the New Jersey Devils this season. He had one goal and one assist in 14 games with New Jersey. He had three goals and six assists in 20 games for the Predators. He has 20 goals and 28 assists in 128 career NHL games.