Novak Djokovic reached the semi-finals of the Australian Open on Wednesday after Kei Nishikori retired hurt when trailing 6-1 4-1 in their quarter-final. Nishikori had a medical time-out between sets, with the trainer working on a right thigh problem. Top seed Djokovic will meet Lucas Pouille for a place in the final. (For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)