The 27 year-old, who currently holds the European title at 160lbs, was drafted in when a unification with WBO champion Dmitry Pirog fell through and a host of possible potential opponents knocked the fight back.
Golovkin, 30, has a formidable record of 20 stoppages in 23 bouts to his name, although Hearn believes that the Kazakhstani will come up against his toughest challenger yet at the Turning Stone Resort & Casino in New York.
“Golovkin is certainly the most feared middleweight in the division,” Hearn told World Boxing News.
“Most top contenders have been offered a shot against him but none, except Proksa, have accepted the challenge.
“He is strong and carries a lot of power, but has never come up against a real live opponent.
“We are about to find out just how good Gennady Golovkin is,” he added.
Proksa has already dismantled former world champion Sebastian Sylvester in three rounds and avenged his only loss last time out when stopping Kerry Hope in eight rounds at the Motorpoint Arena in Sheffield.
‘Super G’ goes into the contest as a 9/4 underdog to overthrow the unified king, with the southpaw aiming to become a name draw in America with a victory and claim two recognised belts into the bargain.