UFC fighter McGregor enters a boxing ring for the first time to take on the unbeaten Mayweather on August 26.
Few in boxing circles are giving the rugged Irishman much hope.
But Holmes, a former world heavyweight champion who keeps a keen eye on the game, feels McGregor has a real chance if he can fight intelligently.
"Don't sell McGregor short, he doesn't have to do too much to win," Holmes told the Bald Faced Truth radio show in the United States.
