Kell Brook and Errol Spence will face off on May 27 at Bramall Lane
Brook will defend his IBF welterweight title against Spence on May 27 at Sheffield United's Bramall Lane ground.
It will be his first bout since losing his unbeaten record having moved up to middleweight to fight the legendary Gennady Golovkin.
And Hearn believes that given how competitive he was at 161lb, Brook is going to be an awkward opponent for 21-fight unbeaten Spence.
Kell Brook looked almost as big as middleweight Gennady Golovkin, according to Eddie Hearn
"We've thought about getting back down to 147lbs [the welterweight limit]," Hearn said.
"We spoke to a nutritionist and looked at the science of it.
"If he does it right, he can make the weight safely and still properly.
Kell Brook lost to Gennady Golovkin on his last outing
"Making it right for him involves taking him away to his training camp in Spain and not leaving.
"He's back here for a couple of days for press obligations but he will stay in that camp to make sure that everything that goes into his body is monitored.
"I'm interested to see the size of Errol Spence.
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"For the Golovkin fight, everyone said Kell was a similar size but a little bit smaller.
"Now back at 147, he is a huge welterweight."
Brook had been in discussions over an all-British fight with Amir Khan.
But negotiations broke down over the purse split and Khan is instead in talks with Manny Pacquiao about a more lucrative bout.
And Hearn believes that Brook-Spence is in fact a far more mouth-watering prospect in terms of boxing.
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"This is the best fight in the welterweight division – no question," Hearn added.
"It's one of the best fights in world boxing with Kell Brook coming in off the back of the loss to Gennady Golovkin and Errol Spence unbeaten.
"He's the mandatory challenger and many felt Kell would look to avoid this fight but he said 'no, this is the fight the fans want' and it'll be at Bramall Lane in front of 28,000 people.
"There are some good names on Spence's record.
"He stopped Chris Algieri in big style and beat Leonard Bundu last time out to become the mandatory.
"More importantly, the bookmakers make Spence the favourite for this fight over Kell in his hometown.
"That should tell you everything you need to know. In the boxing world, everybody knows how big this fight is.
"To people outside of boxing, you need to go away and watch Errol Spence.
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"This is going to be some fight and some occasion at Bramall Lane.
"[Fighting here] is something that Kell has wanted for a long, long time.
"We've worked hard with the club and the council.
"We love stadium events and to bring one here to Yorkshire is a privilege."