On March 28, 2016 it was announced that Mosley would challenge WBA Interim welterweight champion David Avanesyan (21-1-1, 11 KOs) at the Gila River Arena in Glendale, Arizona. on May 28. The winner would then be the mandatory for the winner of the Thurman-Porter fight. Prior to the fight being announced, legendary hall of famer Roberto Durán became Mosley's trainer. This also marked the first time Avanesyan would fight in the United States. At the time of the fight, Mosley was ranked number 3 by the WBA. Mosley lost the fight after going the distance. Avanesyan won all three judges scorecards (117-110 twice, 114-113). Mosley started off the fight quick as the aggressor. As the middle rounds passed, Avanesyan began to take over. Despite the two wide scorecards, the fight was seen as being much closer and competitive.