It was natural for Brennan to start boxing as a child since his father owned a boxing gym. He started to wrestle in high school and eventually became NCAA Division III National Wrestling Championships runner-up and All-American for Johnson & Wales University. Brennan made his professional MMA debut in 2008 and showed his potential by dominating in the local circuit. He was soon picked up by Bellator to win the season nine middleweight tournament. The 27 year old power puncher is on a 3 fight winning streak and is eager to show what he has got to the Japanese fans on NYE.