By Edward Chaykovsky

Promoter Eddie Hearn of Matchroom Sport is predicting a massive upset on September 10th, when IBF, WBA, WBC and IBO middleweight champion Gennady Golovkin defends his belts against IBF welterweight champion Kell Brook at the O2 Arena in London.

Brook secured the fight on Friday in a huge surprise, when negotiations fell apart between Golovkin (35-0, 32KOs) and British middleweight champion Chris Eubank Jr. Brook himself was in talks to face WBO champion Jessie Vargas in a fall unification, and those talks also fell apart.

Now Brook (36-0, 25KOs) will move up by two weight division, thirteen pounds in mass, to take on one of the best pound for pound fighters in the world and certainly the fighter regarded as the top man at 160-pounds.

Hearn is not worried about the weight difference. There is very little difference between Golovkin and Brook from a physical makeup. Brook is a big welterweight and Hearn says the fight kills himself to make the welterweight limit of 147. The veteran promoter also says Golovkin has never faced an elite level boxer in his career - until now.

"This is two weight classes above. I think if it was [taking place] at light middle, I honestly would make Kell Brook the favorite. I think he has a great chance. I think he has a wonderful jab. I think he's going to hit so hard at that weight. I think he's going to hold a shot [better] because he's not going to be depleted. People don't see what Kell Brook goes through to make 147-pounds," Hearn told IFL TV.

"And he is so excited to have a full camp to where he can fuel himself properly. And you'll see what you get on September the 10th. This is going to be a war. Kell Brook is a quality fighter. Gennady Golovkin has never boxed an elite level fighter - and now he is, so let's see [what happens]."