The 30 year-old Yorkshireman takes on the hardest punching fighter – pound for pound – in the world and begins a massive underdog without having been tested whatsoever above the 147 pound limit.
Almost a stone is the usual differential between the two champions, although Hearn is in no doubt Brook can bridge the gap as the Yorkshireman is known to be massive at welterweight and fully struggles to boil down from his walk-about weight pre-fight.
“This is spearheading the new season of world title fights. It’s the biggest fight in world boxing of 2016,” Hearn told Head of Boxing Adam Smith on Sky Sports News HQ at Brook’s media day.
“We’ve been waiting for a moment like this when Kell can show how special he is. He’s doing it at two weight divisions up against the most feared fighter in world boxing.
“He has no fear. When you see the size of those arms and those legs. He’s got abnormal strength and abnormal power. Most of all, he’s got abnormal skill.
“Do not underestimate Kell Brook in this fight. He knows what he’s up against but to be great you have to do something great. It’s like when Leonard beat Hagler.
“Moving from welterweight to middleweight, those are the nights you remember for ever and ever. Kell Brook has the chance on September 10 to be the number one fighter, that’s his carrot.
“It will be the greatest win by a British boxer ever on these shores,” he added.
Both boxers boast unblemished records totalling 71 contests and head towards the World Boxing Council seven-day check weight with intense scrutiny after Brook came in at a whopping 176 pounds 30 days out.