The Welshman travels to Atlantic City as a massive 45/2 underdog, but Hearn has demanded that the former WBA light welterweight champion be shown more respect by the bookmakers.
Hearn, who is managing director of Matchroom Sport, is confident that Rees can cause a "massive upset" in becoming the first man to defeat the highly-rated American.
"I know that [Rees] has been written off," Hearn told a press conference. "Some of the odds we've seen floating around the sports books we actually find quite abusive.
"We're a former British, European and World champion and this is a huge opportunity for Gavin Rees. We know how tough it is, we know what a great champion Adrien is, but we're here to win and not to make up the numbers.
"I can promise the toughest test of Adrian Broner's career. He's a great champion and deserves a lot of respect, but Gavin deserves a hell of a lot more respect than what he's been getting. Him and the team are supremely confident going into this fight and we believe we are going to cause a massive upset and go home and really make a statement for British boxing."
Rees's only defeat came to Andriy Kotelnyk in 2008.