end of round four) to quit in his corner before the start of the eighth round. Pay-per-view return Katsidis' next opponent was Vicente Escobedo, whom he fought on 19 September at the MGM Grand Garden Arena in Las Vegas, as part of the undercard to Floyd Mayweather Jr. vs. Juan Manuel Márquez. The bout was for the WBO interim lightweight title (which had since been vacated by Joel Casamayor, some time following his victorious bout with Katsidis), with the winner receiving a guaranteed opportunity to face the WBO lightweight world champion. In a fight similar to the one with Amonsot two years prior, Katsidis and Escobedo exchanged hard punches for the full twelve rounds, with Katsidis surging forward aggressively and putting constant pressure on the retreating yet accurately counterpunching Escobedo. As per routine, cuts opened up around Katsidis' face early on, together with a visibly swollen jaw in the closing rounds. At the end of the contest, the judges were split with 118–110 and 115–113 for Katsidis and 116–112 for Escobedo. 2010 Return to London Having reclaimed the interim title, Katsidis was made to wait several months to see if a mandatory title bout with Juan Manuel Márquez would materialise. This was dependent on whether Márquez was willing return to the lightweight division to defend his WBO championship, or if he would voluntarily relinquish it to Katsidis in favour of moving up to light-welterweight for potentially bigger fights. By January 2010, Márquez had not yet expressed any desire to defend against Katsidis. A date on 27 March against then-reigning IBF super featherweight champion Robert Guerrero was at one point confirmed for a Golden Boy Promotions event, but Guerrero withdrew from the fight in early February due to family matters. One day prior to Guerrero's withdrawal, Katsidis had turned his attention towards old nemesis Juan Díaz, with both expressing an interest in a potential rematch. On 2 March, a fight between Katsidis and then-undefeated lightweight challenger Kevin Mitchell was officially confirmed by promoter Frank Warren. It was contested on 15 May at Boleyn Ground stadium in London, with the WBO interim lightweight title on the line. At the opening bell, Mitchell looked to establish his jab and keep Katsidis at bay. In the first two evenly split rounds, the occasional flurry of hooks from a highly aggressive Katsidis was enough to make Mitchell fight consistently on the back foot in an