Following the defeat, a rescheduled fight with Juan Díaz was set for 6 September at the Toyota Center in Houston, Texas for the vacant IBO lightweight championship. Over the course of twelve rounds, Katsidis underperformed and enabled a determined Díaz (who had himself suffered a career first loss in his previous fight) to counterpunch and time his attacks with regularity. His face bloodied and bruised once again, Katsidis suffered his second consecutive defeat, with Díaz winning a split decision. Two of the judges scored the fight 116–112 and 115–113 for Díaz, while the third scored it a somewhat controversial 115–113 for Katsidis.