On 17 February 2007, a bout for the newly created and vacant WBO interim lightweight title was made between Katsidis and Graham Earl at the Wembley Arena in London. In an action-packed and fast-paced fight, Katsidis and Earl went toe-to-toe and traded many heavy blows, during which Earl was knocked down twice in the opening round and again in the second. However, soon after getting back to his feet following the third knockdown and having the towel being thrown in seconds later (only for it to be thrown back out again by referee Mickey Vann), Earl managed to floor Katsidis momentarily with a heavy right hand at close quarters, rendering the latter visibly stunned and unsteady on his feet. Earl's comeback would ultimately be short-lived, as Katsidis recovered swiftly and finished the round strongly. At the very end of round three, a low blow cost Katsidis a point, but in the following rounds he went on to deliver a barrage of largely unanswered punches to Earl until the decision was made Earl's cornermen to stop the fight after the fifth round.