Anthony Joshua’s stable-mate Frazer Clarke believed the heavyweight star is mentally stronger heading into his rematch with Oleksandr Usyk. The British icon, 32, had his WBA, WBO and IBF titles ripped away by the unbeaten Ukrainian at the Tottenham Hotspur Stadium in September. AJ and Usyk are expected to meet in a rematch planned for July 23 with the 2012 Olympic gold medallist looking to become a three-time world champion. No location has yet been announced, but promoter Eddie Hearn has declared the blockbuster bout could take place in the Middle East. He told iFL TV: “I think there’s a very…