VIDEO: Anthony Joshua vs Andy Ruiz Jr. First Fight Highlights

Andy Ruiz Jr. figured to be an easy victory for world heavyweight champ Anthony Joshua in his American debut back in June. Instead, Ruiz pulled off one of the greatest upsets in modern boxing history when a ferocious seventh-round performance left AJ unable to continue. With Ruiz now the owner of Joshua's four championship belts, fight fans now set their eyes on the much-anticipated rematch from Saudi Arabia this Saturday. To mark the start of fight week, let's enjoy the best from their thrilling, historic first fight.

Joshua was a perfect 22-0 in his career -- and regarded by many as the world's finest heavyweight -- before Ruiz sent him crumbling to the mat in Madison Square Garden again and again in a fight that had boxing heads thinking of Buster Douglas' stunning upset of Mike Tyson in 1990.

With the scene shifted to the Middle East, Joshua has all of the pressure on him, as he needs to avenge his loss to the underdog Ruiz if he wants to keep his place among the heavyweight's elite. At this rate, a loss would be simply disastrous for his career.

Joshua was expected to walk over Ruiz without any special effort the first time around, but one third-round punch right on his ear rattled him to the core and threw him entirely off his game. His dream of one day claiming the undisputed heavyweight championship was deferred, and if things don't go well for him Saturday, they could be over forever. AJ might have all the talent in the world, but Ruiz has the momentum (and surprisingly fast hands!) on his side. Rest assured, their big-time rematch will shape the future of the division one way or another,