ALL Black Eric Rush, rated one of the finest sevens rugby players in the world, is in doubt for the Hongkong and World Cup Sevens. A recurring injury forced him out of the Singapore Sevens on February 21, where his Takapuna side went down 28-12 to South Africa's Durban Harlequins in the quarter-finals. Rush, who was plagued by hamstring and back injuries last season with the All Blacks in South Africa and the touring New Zealand Maori side, was grounded in Singapore by a Japanese player, Tony Kubo. Kubo apologised to Rush after the tackle and immediately asked to be photographed with him. ''Rush is my idol and now I'll have a story to tell when I get home,'' he said.