By Frank Dalleres Defending champion Novak Djokovic admitted he had been given a run for his money after coming through his longest Grand Slam first round match at the Australian Open. Djokovic needed more than four hours to finally see off 18-year-old Croatian Dino Prizmic 6-2 6-7 (5-7) 6-3 6-4 and extend his winning run at Melbourne Park to 29 matches. “He’s an amazing player, so mature for his age,” he said of Prizmic. “This is his moment and it could easily have been his match as well. He made me really run for my money. “I’m double his age. Reality hits hard tonight. I struggled in many d…