In his next title defense, at on November 21, 2008, Southworth lost the light heavyweight championship against former UFC Light Heavyweight fighter Renato Sobral "Babalu" by TKO (cut) of the 1st round at 5:00. Southworth was winning the round, having scored a takedown and controlling the clinch, until "Babalu" opened up a horrendous gash above Bobby's left eye with ten seconds to go. "Big" John McCarthy stopped the action to let doctors inspect, and Southworth finished the round by dropping "Babalu" with a punch just before the bell. However, when doctors got a better look at the wound between rounds, the fight was stopped due to the size and depth of the cut. Southworth announced he would like a rematch and Sobral verbally agreed, however a rematch was never organized and following Sobral's 2013 retirement it is unlikely a rematch would ever occur.