Joshua will be looking to regain his IBF, WBA, WBO and IBO belts after suffering defeat to Ruiz in NY earlier this year, but the British Heavyweight will have the backing of thousands of United Kingdom fans joining boxing enthusiasts from more than 60 countries across the world.
Klitschko was defeated by Joshua in 2017 at Wembley Stadium with a technical knockout and the two boxers have stayed in touch even after the Ukrainian retired later that year at the age of 41.
Heavyweight champion Andy Ruiz Jr said Monday that all the pressure will be on dethroned champion Anthony Joshua in their contentious showdown in Saudi Arabia.
"I spent six months in the gym and that's why you see a boxer's lean physique", Joshua told Sky Sports in the United Kingdom amid questions over his more athletic appearance.
"We've got to see where he's at because all the pressure is on him".
Speaking about the diversity of ticket sales, Frank Smith, CEO of Matchroom Boxing, said: "The matches in which Anthony Joshua participated achieved record sales around the world, whether in London or NY".
"I'm expecting that", he said.
He added: "This upcoming match is one of the biggest boxing fights in the world". I feel at home you know. "I've got to show my skills, my talent". "The hard part is over, it's time to have fun on December 7".
Ruiz Jr has suffered only one defeat in 34 fights, losing a majority decision to Joseph Parker in 2016. Sometimes fighters lose, it makes them weaker. "I hope he wins, I want him to win, but if he wins or not, it's a different thing".
Ruiz Jr shocked the boxing world with his win but Joshua exercised his contractual right to a rematch nearly immediately and just weeks later, the sequel was confirmed to take place in Diriyah, a small town on the outskirts of Saudi's capital Riyadh. "I know I can do it", Joshua said.
"Win, lose or draw he has a future", Hearn told Sky Sports.